Personally, reading strictly what is in the rules and not what other people have said outside the rules (including Phil!):-
1. All movement is measured "as the crow flies", start point to end point and measuring front corners (not back corners, which means that a single element that turns a 180 in the course of its move appears to gain/lose a base depth).
2. There is nothing in the rules themselves about not dog-legging around a TZ. Personally, I think Fig 9a shows the Cv dog-legging outside a TZ in order to avoid the effect of Bd A's TZ. If there is a strict rule against dog-legging around TZs, getting a reserve line into combat is normally impossible. For example, two ranks of Reg Bd approach enemy who are (as is normally the case), parallel but slightly offset. Rank 1 hits and conforms to the enemy with a shift to one side. Rank 2 is now unable to move into any casualty-gaps in one move, as a dog-leg is required to line up. Don't even try to have an effective reserve of Cv/LH that is less than a full battle-line's worth.
Phil may well add something in for DBMM v.2 once Book 4 is published!
3. The Commentary has added a Suggested Playing Convention that elements should not move further than their allowed move from their starting position. It's not an ideal solution but does remove the worst of the "quantum tunnelling effect".
4. In competition-play, an umpire ought to step in to resolve any situations where an unscrupulous player might be trying to take an unfair advantage.
Playing this way, I have never seen anyone try to "quantum-tunnel". Fears of such activities are groundless, IME (i.e. I have never yet met an unscrupulous player and don't currently expect to, at least on the UK competition scene). The closest I have seen is an incident at Milton Keynes when an element of Cv moved from the front of a group to the rear of the same group (miles away from enemy TZs). Measuring "DBM-style" it exceeded its move. Measuring straight-line it was fine. The effect was that it appeared to the literal-minded to interpenetrate its friends. In practice, if you imagine the troops making the move actually riding around their friends to take up their position it was perfectly logical.
Just do the maths at some stage and work out how fast troops are actually moving in the 10 minutes of each bound and you'll see that even LH don't break the dizzy heights of 1mph (320pp at 2.5 feet/pace = c.267 yds in 10 minutes = 1600 yards/hour. There are 1760 yards/mile. Of course, since elements don't move in the opposition bound, you can in fact halve even this blistering pace...). As you can see there's a lot of scope within the game-model for elements exceeding their "permitted" move allowance in terms of the path followed without breaching the laws of reality!
DBM(M) is a very abstracted game, don't get too hung up on assuming that troops have their feet nailed onto 60-metre wide bits of board and wheeled around a battlefield on castors, and try imagining that they are a group of individuals (and their mounts) going and doing what their unit commanders tell them to do. The troops within elements "flow" in reality, the sub-units charge and follow the easiest path to get to where they want. Move distances are a game-construct which in no way reflect maximum actual man/horse speed.
Tim Child