Buddy of mine got burned the same way, fake burrs are everywhere now.

My only rule is if the case smells like a basement, it's a keeper lol.

Yeah the 2x4 thing got me too, and I found out pretty much the same way, some guy half my age just casually dropped it on me. What helped me after the initial anger wore off was grabbing a little pocket notebook and actually measuring stuff before I trust the name. I marked down real sizes for 2x4, 2x6, 2x8, 4x4, and even plywood thickness since that's another liar (3/4 ply is not 3/4, it's more like 23/32). Every time I go to the yard now I check a couple boards against my notes because they can vary a little by supplier and how dry the wood is. The spacings thing is real too, I redid my railing math once and was off by almost two inches over eight feet, so it does sneak up on you. Just write it down and keep it in your truck, saves you the headache later.