In the inventory textures of spore blossom, big dripleaf and small dripleaf are 3d, even though textures of all types of non-full block vegetation are 2d:

• crops (wheat, potatoe, carrot, beetroot, sugar cane)
• seeds (wheat seeds, melon and pumpkin seeds, cocoa beans
• grass and tall grass
• fern and tall fern
• red and brown mushrooms
• nether spores and roots
• twisting and weeping vines
• nether fungus
• nether wart
• sweet berries
• glow berries
• glow lichen
• vines
• bamboo
• sea vegetation (kelp, sea pickle, seagrass and tall seagrass)
• chorus friut

Also these items in 3d just look kinda werid, especially the spore blossom.