Hard to say if they're getting "enough' because no one really knows how much is "enough" to begin with.
He gets fed Zupreme canned monitor diet (which says it already contains vD3) mixed with veggies 2x weekly and once a week, he just gets a little veggie salad with some vitamins sprinkled on top.
He is large, but not obese. And I always examine him to make sure he is not suffering from any form of MBD.
I've talked with several breeders doing this with bearded dragons and monitors, providing no exposure to UV lighting, and their animals breed like crazy and produce viable offspring year after year.