I am still experiencing a form of this bug in 1.16.20
After a little while absolutely no kelp will grow in my observer/piston based kelp farm - it gets stuck on 2 high (just in front of the piston) so it's never seen by the observer. As far as I can tell it's not even just growing "slower" - after hours even with increased tick rate none will grow. A timer based design seems to work, however (since the kelp always reaches 2 high.)
I put it in BDS because it's only been an issue with BDS, never when playing Bedrock only - it's as if the server isn't prefetching the chunk you'll be loading into. No idea which side causes the problem, so that was just my best guess
I am still experiencing a form of this bug in 1.16.20
After a little while absolutely no kelp will grow in my observer/piston based kelp farm - it gets stuck on 2 high (just in front of the piston) so it's never seen by the observer. As far as I can tell it's not even just growing "slower" - after hours even with increased tick rate none will grow. A timer based design seems to work, however (since the kelp always reaches 2 high.)