Interesting question. They made popular music, so they are pop in that way, but is Helter Skelter a pop song? Is when I'm sixty Four? Yellow Submarine is a children's song. For me genres should just be an aid to talking about music,If I say Prog rock you know I'm talking about Yes, early Genesis, ELP et al. But none of those groups set out to make prog rock and they all have very different sensibilities.
The Beatles if they are typified by anything it is the range and variaty of their music, Yesterday, Come Together, Here Comes the Sun, I want to Hold Your Hand, Ob la de ob la da, Being for the Benefit of Mr Kite.
If I think of a perfect pop group, I think of Abba. Their songs all can be described as excellent examples of pop. Try to put a label on the panoply of Beatles music and the label will break.
edit: I just remembered when Paul was talking about Yesterday he made the comment that at that stage they thought of themselves as a little R&B combo.
Labels are only useful to the extent that they help us describe things and pop music doesn't help describe the Beatles, it is the other way round The Beatles extended the bounds of popular music. But popular music in this sense is not a genre, it's not that same as "pop music"