No, you don't need the crown board holes for ventilation - best to close them off anyway whenever you're not using them for feeding. Majority consensus (you'll have learnt already that beekeepers never agree anything unanimously!), and common sense, is that bees are better overwintered without any top ventilation and with a nice slab of insulation on top of the crown board, under the roof.
Just like you at home, the bees don't want to lose all of that heat they've generated through gaping holes above them.
I keep a slap of 50mm insulation permanently glued into my hive roofs all year round. Going into winter most of my hives get a second slab of insulation in an eke between the crown board and roof so that bees have 100mm of insulation above them in total, but that's just me being overly protective
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