Why does a nuthatch eat upside down?

Why does a nuthatch eat upside down?
Bonners Ferry Herald - Outdoors, Nuthatches: The upside-down bird
Jun 4, 2019

Red-breasted nuthatches readily eat seeds from bird feeders and they tend to pick the heaviest seed. ... While woodpeckers search for insects by spiraling up a tree, the nuthatch zig-zags down the trunk head-first. Foraging upside-down may seem unnatural to us but nuthatches have a knack for it.

[marktalbott]

They don't always eat upside down. I have them come to my feeder all the time. They mostly do that because they're used to going up and down trees. But they'll sit on my feet and eat while sitting upright. So the notion that they always eat upside down or there's a reason for it is stupid