I think he's saying that there appeared to be a bug in some taggers that didn't calculate or write the ID3v2 tag length correctly in the ID3v2 header, and it appeared as if it was just a bunch of garbage. The mp3 sync is 11bits long, but the ID3v2 spec specifies that data can be presented in such a way as to never match that sync, so as to comply with players that don't understand ID3v2.