Crimson and warped stems are part of the Building Blocks category, whereas mushroom stems are way off in the Decoration Blocks category, which I don't think is right, since I'd expect all the fungal stems to be in the same place.
Nether and warped wart blocks do not come after leaves in the Creative inventory
Sort order of creative inventory confusing
Ancient debris is not grouped together with other ores in the Creative inventory
Stone and polished blackstone buttons/pressure plates are located at opposite ends of the spectrum of buttons in the Creative inventory despite being identical in behaviour