Can't walk down L-shaped stairs with 2-tile desk underneath

Not sure if this is a bug or a weird feature.

I tried to put a a 2-tile desk under a L-shaped staircase (using bb.moveobjects). The desk itself was fine, and I could use the computer on it without issue.

However, the sims could not walk down the stairs (walking upstairs works mostly, but sometimes not?). Now, if this was just a matter of "putting stuff under the stairs makes them unusable" that would be ok. Annoying, but ok. But after some testing I noticed the following:

(all test done with short wall height)

1. With a straight staircase and a 2-tile desk underneath, the stairs do work.

2. With a L-shaped staircase where the bend is in the upper half of the stairs and a 2-tile desk underneath, the stairs don't work.

3. With a L-shaped staircase where the bend is in the lower half of the stairs and a 2-tile desk underneath, the stairs do work.

4. If you put 2 1-tile desks next to each other, in the same space a 2-tile desk would go, the stairs do work, regardless of the shape of the stairs.

The thing that confuses me is no. 4. If it was just the amount of space under the stairs that caused issues, then 2 smaller objects that take up the same smount of space as a big object should cause the same issues that the big objects does, right?

I use windows 10. Game version 1.69.59.1020. All currently released packs installed.

I have some mods installed, though very few build-/buy-objects, and I tested the above in a new save file after removing all my mods and got the same result.