That statement, Robin, only refers to the situation when the units are already in the minefield, not the latter situation described when entering a hex to clear mines. You left out the part stipulating 'in a minefield location.'
No, I stand by the statement that the rule for the entering of a minefield is not absolutely crystal clear about which phase this is allowed. The rule simply speaks about using the entire MF. However, there is no way I would personally interpret that going TI is something you can do when advancing, as it is supposed to represent activity over an entire turn.