When attempting to replace seagrass with a regular block such as a grass block, gold block, etc. the sea grass is deleted as one would expect and replaced with the intended block. However, this does not work at all if the block attempting to be placed is a conduit or kelp. The placement will fail regardless of whether the plant is targeted directly or an adjacent block is.
Linked issues
relates to 2
Comments 4
Possibly relates to MCPE-33346
Relates to MC-132816
Can confirm for 1.13-pre4.