Steps to Reproduce:
 Step 1: Place any of the tall flowers (sunflower, lilac, rosh bush or peony) on the ground.
 Step 2: Pressing F3, then look at the tag of the tall flowers, you will see that they're in #replaceable_plants tag.
 Step 3: Place any block onto those tall flowers.

Observed Results:

Tall flowers are in #replaceable_plants tag, but they don't replace when try to place block onto them.

Expected Results:

Tall flowers are not in #replaceable_plants tag, and they don't replace when try to place block onto them.

Or:

Tall flowers are in #replaceable_plants tag, and they replace when try to place block onto them. (this possibility is less likely because 1 block tall flowers also don't replace when try to place block onto them.)