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 view Profile -> Achievements, the setting is ignored.

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 viewing Achievements as it seems to be re-reversed back as if the A/B Button Swap is disabled, when in fact it is actually enabled.

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

https://bugs.mojang.com/browse/MCPE-132194