A potion of weakness is commonly brewed by directly adding a fermented spider eye to a water bottle. However, awkward, thick, and mundane potions work as well when brewing potions of weakness, which is not intended in Java Edition. Thick and mundane potions are also likely to be designed to have no brewing usage, so this is probably a bug.
MCPE-140342
Potions of weakness can be brewed using awkward, thick, or mundane potions
Open
2
Confirmed on 1.17.30.25 (Android).
I would like to say that this disparity is rather trivial in that it requires the player to waste resources.
I checked further and this is the only potion that can be made with thick or mundane potions in Bedrock, so the brewing process is not broken (except for the abovementioned single case).
Apologies for late confirmation report.