Confirmed — your screenshot shows the overall and the pants both worn, which shouldn't be possible.

The rule was only implemented in one direction. Putting an overall ON correctly kicks your pants back into the bag. But putting pants on while you're already wearing an overall did nothing to the overall, so you ended up in both. An overall covers the top and bottom slots, so wearing pants underneath has to remove it.

The patch adds the missing half: pants going on now push the overall back to your inventory, and it goes through the same all-or-nothing space check the other direction uses, so it will refuse rather than lose your overall if the equip tab is full.

Small extra detail you may have noticed: if you had logged out and back in while wearing both, the pants would have vanished from the pants slot. That's a clean-up rule that runs on load and it was papering over this bug — it'll stop firing once the equip rule is right.

Confirmed and fixed. The rule was only wired one way: putting an overall on already pushed your pants back into your bag, but putting pants on while an overall was worn did nothing to the overall, so you ended up wearing both — which is what your screenshot shows. Now it works in both directions, exactly as v83 does it: pants pulled on over an overall send the overall back to your bag. If your equipment tab were somehow completely full at that moment the overall stays on rather than being duplicated or dropped, so nothing can be lost. Note that any character who is already wearing both from before this fix will sort itself out the next time either piece is re-equipped.