Yeah I would suspect that vegans would be slightly shorter than their omni counterparts, if you could compare a decent population of vegans (say 100,000 covering all demographics), with the same number of omni's etc.
However we'd be a hell of a lot lighter thats for sure! Mostly due to the fact that vegan diets aren't as energy dense and generally contain more fibre etc etc. Some of my omni cycling friends stop training and in no time at all have put on 5kgs. I slob around for half a year and I put on 2kgs which seems to be about my ceiling. Not that I'm complaining!
Maybe there is something in dairy that makes people grow taller than they otherwise would? A cow is 440kg (av NZ dairycow) and produces milk perfectly suited to their calves, which grow a hell of a lot quicker than their human equivalents! Or again is this just mostly due to milks calorie content?
Genetics is the main factor I would suspect. My partner is 5ft4 and her sister is 5ft10

Both had exactly the same diets etc. To look at them you'd hardly even think they were related.
I used to drink gallons of milk as a kid, as I refused to drink the local yukky tapwater and from the age of 5 would have consumed
at least a pint a day. Didn't make me any taller unfortunately as at 5ft11 am the shortest man in my family. Both my Mum and Dad are tall...Damned brother is 6ft2! Grrrr! I feel duped!
Anyway will be interesting to see how tall my son gets. Theory versus reality and all that
