I started noticing this on Nintendo Switch but I've found that it affects all Bedrock Edition platforms.

If you enable the A/B Button Swap in-game (under Settings -> Controller), then sleep in a bed, the setting is ignored (Leave Bed / Open Chat buttons).

With the setting enabled, the B button should be ACCEPT and the A button to CANCEL. This is the correct action for most areas in the menus. However, this doesn't seem to be the case when sleeping in a bed as it seems to be re-reversed back as if the A/B Button Swap is disabled, when in fact it is actually enabled.

If you highlight Open Chat, then press the B button to accept, it backs you out instead. This causes you to stop sleeping.

There might be other areas in-game where this setting is being ignored as well, including:
MCPE-132193