1...2...3...4...1...2 ("3, Gooo!") *start funky guitar music and drums*
I used to have the MFSL version (now I have
Revolver [Dr. Ebbetts PMC 7009; Matrix XEX 606-1]), and in every version I heard (sans today's loud, conpression iirc), it indeed starts quieter than the main song.
It's intentional, don't worry. 
Oh, it's noticeable on "Here, There And Everywhere" too? Nope, this song is pretty much the same volume the whole way through.