Long before I was staff or was friends with anyone who was, I made my own graphics and never once had an issue.

Here's one place where I agree more with you - it's not explicitly stated that you can't use items from the tileset, but in most cases it isn't allowed.

Some would say it falls under " only upload graphics that you have made yourself or that you are authorized to use" but I'm going to say it's for other reasons. A lot of people try to build disguises or fake buildings / etc with those, or they make blocks of solid black or whatever. And when they spam them, they are upload banned.

If a staff member uploads something of their own that otherwise wouldn't be allowed, they're not going to have upload rights for long.