Yes, copyright issues, not from the Fab Four or PBS. The owners of the songs or records (indistinguishable from the real Beatles’ records). Apparently someone at RU-vid or song owners decided it was better for them NOT to block it.
When you have two guys such as Gavin and Adam who are from the homeland of The Beatles, it adds a lot more authenticity to the group in terms of re-creating the look feel of The Beatles. Plus they'd be able to bring it home because not only are The Beatles a part of their culture, they're a part of their lives and they'd be able to add some personal insight to their performances as well.