well it's because he's also a painter. However he learned his skills from cake decorating, which uses a lot of the same skill sets. It makes sense but if youve never decorated a full on cake it's understandable that it's confusing. Hope this clarifies
Makes sense if you think about it. If you add a patch to a piece of clothing, you'll see seams around the edges. To "seamlessly" blend in, there'd be no edges, it'd be perfectly smooth and undetectable.