Boats placed underwater float to the surface instead of sinking

Summary:
Boats used to sink when placed underwater, which was intentional according to MCPE-8863. At some point, boats stopped doing this and they now float to the surface instead. This does not match Java Edition.

Steps to Reproduce:

1. Locate an ocean

2. Go underwater and summon a boat

Observed Results:
The boat floats to the surface.

Expected Results:
The boat sinks.

Video: