Not trying to be critical, and her squat form is definitely not good (she looks like she's nearly doing a good morning on the way back up!), but powerlifters use this technique a lot and would actually say you shouldn't breathe out until you reach the top - if you do it properly and breathe through your diaphragm, it helps to brace your spine, especially for heavy sets with lower reps (or that's what I've been told by coaches anyway).
For high rep/lower weight, you could usually breathe through the movement, though, because you don't need as much power/brace, but I tend to breathe in and out at the top regardless.
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