Can I stick my two penn'orth in here?
In an interview in 1979, John describes RockWrok as "a simple celebration of sex. The idea of the song is a take-off of what rock'n'roll is all about. And it's meant to be structured like a 1920's porn movie. Very jerky and quick. Lots of images all thrown in together."
Billy agrees, referring to the song as light-hearted and comical. There's even a suggestion that Charlie Chaplin can be imagined doing some of the things described!!
Personally I think there's a bit more to it than that, as I have mentioned on a similar thread about My Sex. I reckon this song reflects the explosion of sex and music that happened in early 1977.
As for the spelling, I would imagine John just liked the play on words and was being deliberately tongue-in-cheek about it.
I wonder if there is also the remotest nod to Kraftwerk's piece "RuckZuck" from 1971, which translates (I think?) as "hurry up" or "do it quickly" - seems to make sense with John's description above.
That track is spelled with a capital 'z' as I think RockWrok is. Maybe that's the mispelling of the title John referred to??