He didn't claim the money bag logo was his. He saw an opportunity, trademarked it - then collected cash from anybody that used it. I doubt Teenage Fanclub knew anything about it. Their label will have just done a deal and it won't have been a big deal, otherwise they would have changed the cover for subsequent pressings & not used the image on T-shirts etc.

He had been using it as the logo of Simmons Records for several years before Bandwagonesque was issued.