I guess I've always taken the route that once marked with a TI counter the unit was engaged in the act of clearing the obstacle (i.e. using Clearance) and would therefore be subject to concealment loss at the end of its MPh because it would be considered a moving unit utilizing all it MF to accomplish the task and would therefore be subject to concealment loss for that reason. However, you do raise a valid point by strict wording of the rules as presented, but believe if a clarification was warranted, it would come down on the side of concealment loss at the time it was declared and thus MF spent. JMHO.