I found this rather lengthy response by Perry to snap shots in Klaus's compilation. It gives me pause to think that the OP is correct to think that shot is allowed.
A8.15 Using ABTF map for the following examples. The firer is in V6. The target moves from T3 to U4. Snapshot at the T3/U4 hexside. Does the target receive the hedge? The orchard? Both? Same shot, reversed, target moving from U4 to T3 – identical DRM?
A. Yes. No. No. Now orchard also counts.
Make T4 rubble. Moving from T3 to U4, is the snapshot blocked? Is it hindered? Moving from U4 to T3, is the snapshot blocked? Is it hindered?
A. Not blocked (the LOS has entered, but not exited the Rubble hexside). No (the target is not in the rubble hex). Yes (the hexside is crossed by the LOS). NA.
Firer in S4. Target moves from U1 to T1. Does the wall apply? Target moves from T1 to U1. Does the wall apply? A. Yes to both. Firer is in S3. Target moves from P4 to Q4. Does the hedge apply? Target moves from Q4 to P4. Does the hedge apply?
A. No, target is in Q4 and LOS doesn’t touch P4 before reaching the vertices. Yes, target is in P4 and LOS touches Q4 before reaching the vertices.
Firer in T16. Target moves from V14 to U14. Does FFMO apply? Target moves from U14 to V14. Does FFMO apply?
A. No to both per A8.15 “FFMO DRM cannot apply”.
Firer is in X17. Target moves from V18 to U19. DRM? If V18 was rubble, would there be LOS and if so what would be the DRM? Target moves from U19 to V18. DRM? If V18 was rubble, would there be LOS and if so what would be the DRM?
A. +2 (Orchard + hedge). Yes, (rubble + hedge TEM). 0. Yes, rubble TEM.
Ver. 22 A8.15 A squad assault moves from bL3 to K3. Firers in M2, L1 and M1 each want to take a separate snap shot. Are any of these firers affected by hedge TEM?
A. No; A8.15.
Likewise, if the squad were in bypass at bL3-K3-K4 and M1 fired at it, would hedge TEM apply?
A. No; the LOS does not pass _through_ K3 (the hex that the hedge hexside shares with L3).
And finally, if a squad is in bypass at bI4-H3-H4, when would hedge TEM apply – would it apply when the LOS passes through H3 or H4? Or would it only apply if the LOS came along the H3-H4 hexspine? A. Only if the LOS came along the H3-H4 hexspine. A8.15 & A26.11 If a unit is affected by a Snap Shot and broken as a result, would it nevertheless gain Control of the otherwise empty location it was about to enter as it “is considered to be in the location entered thereafter” per A8.15? Is there any difference in the same situation if the Snap Shot result would have been a “KIA”?
A. Yes. No. A8.15, B9.2, C.5, & C.5C
If a unit in 11D7 moves to 11C7, and a unit in 11G9 takes a snapshot at that moving unit along the D7/C7 hexside, is the LOS blocked by the hedge? If not, does the tem apply?
A. No. Yes. (A8.15 specifically mentions that the hedge hexside “...of a hex being entered/exited can modify a Snap Shot if crossed by the LOF on the way to the target hexside”.)
Would this be an exception to the B9.21 example? It seems to be a very similar situation (LOS to a vertex/hexside). Would that be a range 3 attack or range 4 attack?
A. The target is considered in C7 for range purposes but the attack is occurring at the hexside, unlike in B9.21 where the hypothetical is clearly in the further hex.
{1} A8.15, B9.2, C.5, & C.5C Assume that the 467 in 2Z3 enters 2AA4, and that a hypothetical DEFENDER in 2X2 that makes a Snap Shot attack at the Z3/AA4 hexside. 1) In the above situation, “the hex the target would remain in if affected by that fire” is the hex entered (AA4), so C.5C can be read: “The hex containing the target is the hex entered (AA4)”. Does C.5C therefore say that the 467 is considered in the hex entered (AA4) for Snap Shot purposes? If no, what is the meaning of C.5C?
A. Yes.
2) Range: C.5A defines the range to always be counted to the hex entered (AA4). Correct?
A. Yes.
3) Covered Arc: If a hypothetical MG with a fixed CA (A9.21) has the hex exited (Z3) inside its CA, but not the hex entered (AA4), a snap shot is not possible (according to C.5B). Correct?
A. Correct.
4) Walls/Hedges: B9.2 says that a wall/hedge blocks LOS unless the wall/hedge is part of the target hex, but A8.15 says that a wall/hedge hexside of a hex being entered/exited can modify a snap shot. This is to understand that such a wall/hedge hexside can never block the Snap Shot LOS, so for snap shot purposes the LOS is clear regardless of which hex the target 467 is in. Correct?
A. Yes, if I understand your question correctly. Basically, since the Snap Shot is made at another hexside of the same hex (Z3) with the original wall/hedge then the LOS is not blocked (though wall/hedge TEM for that original wall/hedge will apply).
5) Rubble: The same A8.15 sentence applies similarly to Rubble, so if Z3 and/or AA4 contains rubble, the Snap Shot LOS is not blocked, but is affected by Rubble TEM, and the highest if one contains Wooden Rubble and the other Stone Rubble. Correct?
A. In your EX, rubble in Z3 would affect the Snap Shot; rubble in Z4 would not since it is not “...crossed by the LOF on the way to the target hexside.”
6) SMOKE: 6a) The same A8.15 sentence applies similarly to SMOKE, so if Z3 or AA4 contains SMOKE, the LOF is affected by the SMOKE. Correct?
6b) If both Z3 and AA4 contains SMOKE, are both added as DRM as per A24.2?
A. Only if there is SMOKE in the hex “...crossed by the LOF on the way to the target hexside”; so only SMOKE in Z3 would affect the Snap Shot in your EX. SMOKE in AA4 would be ignored, per A8.15.