The majority of switching controllers, these days, implement a low cost over-voltage protection (OVP) function via primary side auxiliary winding on the transformer. Whether or not the engineers cared enough to properly calibrate it and/or design the transformer for good repeatability...well, that's anyone's guess.
That said, a few years ago, my brother bought a $5 turd power supply for his laptop off eBay...and while we can't definitively point a finger at the power supply, the laptop stopped working a few months after. So, when it really matters, just get something decent, if you are worried about reliability. They aren't that expensive if you get something from Meanwell, Delta, CUI, etc..