KTmum,
Adrian doesn't hold his bottle either. He'll do it once in a long time, but holding bottle is my job. He takes and drinks from sippy cup, cup with a straw and regular cup on his own, but not the bottle.
So, I don't think it's a problem. I figure, he'll stop using the bottle soon, so it's not a big deal, as long as he drinks on his own in the high chair.