Man, that guy at the depot did you a real favor. I got burned once on a move where the fender came back scratched and I had maybe two blurry pics from my driveway, so the claim went nowhere. Now I walk the whole car, shoot a slow video plus pics of all four corners, the roof, and the dash with the miles showing, then email them to myself so there's a date stamp.

Sounds like you just learned something every concrete guy knows already, but ok. Waiting an extra 40 minutes is not some big secret, it's just paying attention to the mix instead of being in a rush. I've seen guys pour in 95 degree heat and still get a clean finish because they knew when to stop working it. The temp changes things, sure, but it's really about not jumping the gun. If a chalky slab surprised you, that's more of a you thing than a weather thing.