I get your frustration but from a technical point of view :
I’m not saying this IS how it’s done but it COULD be
Ladder \/
| - | A
| - |
| - |
| - |
| - |
| - | B
The program is probably something like, sim move from a to b
If you cancel the action, the sim can’t be like a.5 it would have to continue and then reverse
Down the ladder : sim move from a to b
Cancel : reverse (so you end up where you started because you clearly didn’t want the sim to go up the stairs)
It’s already actually quite cleaver if you think about it. You cancel the sim from going up the ladder or stairs so it makes the sim stay at the bottom, they could’ve just made it stop at the top but they didn’t.
Try and appreciate the sims team & their work more, it isn’t so easy