The hitbox is too small for the flowers - Tulip (all), Lily of the Valley, Poppy, Blue Orchid, Allium, Azure Bluet, Mushrooms (all), Cornflower, Oxeye Daisy, Dead Bush, Seplings (all) and Wither Rose.
With the Sunflower a whole block is calculated although it is not wider than a tulip.
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Affects 1.16-rc1
Can confirm in 21w06a.
Can confirm in 1.19.4 Pre-release 1.

Can confirm in 1.21.4.
MC-3073