They aren’t really designed for breaking. I cut them with sidecutters and tidy them up with a scalpel. It wastes one or two each time, but they are cheap.
Those only accept machine pins, though. You can’t use them to plug on to .1" header pins, so their usefulness is limited.
I’m not certain why they are labeled breakaway as they are clearly not from the pictures. I have breakaway female headers and they actually have break lines and snap apart cleanly similar to the male ones.