Oh, that's a very specific crack. This is an extrusion error. The extrusion temperature is dropping too low while it's still over the internal die. The thicker peaks cool more slowly than the thinner flats, remaining at a weaker temperature longer, and they're pulled apart by accumulating contraction.

These cracks usually aren't obvious until they meet a conflicting load. For example, tapping threads up the end without supporting the work correctly. It's not like this is a load bearing part, they could get around this issue with a little care. Holding the work in a hex collet during tapping is cheap, adds efficiency, and would solve the problem. Sending feedback to the extruder is free and usually effective. Or maybe the product is moving well enough on brand equity that it's not worth bothering.