The bug

Rose bushes, peonies, lilacs and sunflowers are part of the block tag #minecraft:replaceable. This means that they do not block line of sight from an enchanting table to a bookshelf.

Due to the Works As Intended resolutions of MC-261613 and MC-261618, I am led to believe that this case is the issue. Removing these four blocks from the block tag would also "fix" MC-255846.

How to reproduce

1. Create a valid enchanting setup
2. Fill it with one of the four species of two block tall flowers

Expected results

Since pitcher plants and one block tall flowers block the enchanting table from interacting with bookshelves, these four species would also do so.

Actual results

They do not.

Further notes

Tall grass and large ferns must remain part of this tag due to them being actually replaceable.