I think the biggest reason for not allowing it to be cycle-dependent is that then you have both behaviours, the crowd can follow or they fall, and a new player encounters one behaviour, learns that, then gets confused when a level relies on the other behaviour. It's not intuitive at all to think that it might be cycle-dependent (unlike the builder-into-miner case where it is easily visible that sometimes the builder can place a full brick just touching the wall and sometimes he can't), so the player has no reason to guess that it might be.
If we change the platformer to have a single behaviour, the next question is what it should be. Normally, with no teleporter, a platform stays at a single height and the crowd can always walk across it; so the crowd being able to follow is definitely the expected result, and consistent with the idea that teleporters transplant the skill to a new place without changing its properties.
The only reason against doing this is that it creates an inconsistency with builders, unless we change the behaviour for both of them. And since this is a niche behaviour that very few levels rely on; and it is unexpected, counterintuitive and feels like a bug; I think that changing it for both builders and platformers would be the best decision.
(Obligatory grump about how making teleporters revert lemmings to walkers would be even better, but I agree that would break too much existing content to be considered at this stage.)