I do understand your point, but I do not agree with it. You say most people can sing a chorus of a beatles song. I think most non-musicians could memorise a few verses of Beatles songs in an entire week (considering they are already familar with the melody and everything, and already know the chorus). Even if somebody had been living in a weird universe that had every form of music except for the Beatles music.... It wouldnt be hard to memorise the lyrics to She Loves You, Help, Let it Be, Hey Jude or any other of their "simpler" songs.
But these guys are musicians. It is part of what they do to learn songs. I think the ones who said they are not familar with the Beatles music are ignorant.