Hunting Food Plots Question

Disclaimer going in-for years I've hunted over feeders or in thick shite, so I'm a novice at hunting greenfields/food plots. My cousin and I were taking last night-he thinks when the greens are covered with ice or thick frost that the deer are a lot less likely to come to the fields than to go scrounging in the woods for remaining acorns or other browse. Judging from having seen zippo over one of the prettiest food plots I've ever seen two mornings in a row, maybe he's right?