What's the basis behind these Tallhous in Touhou fanon?
If its general fanon then its just because there are few characters with confirmed heights by ZUN but even then they are obscure like "fairly short" or "average" so artists have to interpret heights themselves (with characters like the Scarlet Sisters, fairies, Tewi, Kisume, Sukuna etc generally being interpreted shorter and characters like Meiling, Ran and Yukari, Yuugi etc being taller)
As for these "Tallhous" I guess setz just wanted to throw the usual consensus out the window and make characters quite different then what people usually interpret them as. For example: As for fan interpretation Kagerou seems to be fairly tall with the other two being average height but here setz just does whatever. This concept of his seems to go back to post #1289243
