Hear people casually mention using non-OEM parts all the time (which is fine), but never telling the buyer? That's wild. Like, putting in aftermarket brakes and not saying a word crosses a major safety and honesty line for me. The line is basic transparency, full stop.
Honestly depends on the part and the install. Some aftermarket brakes are way better than stock. If the work was done right, it's not always a safety thing. The real issue is just not knowing what you're buying.