Fair enough, I was curious about that point too (but maybe they were working for govcloud, which probably has more onerous background checking).
Every single job I've had in California for the past 30 years (from academic software engineer to computer scientist to industry software engineer) has clearly stated that they do not drug test before I signed any paper. In fact, my manager at Lawrence Berkeley Lab (RIP) was specifically sent there after he refused to take a drug test at a more serious DOE lab, "so he could fit in with all the other hippies and druggies".
I can't speak to any of the other roles, although in my time in the food service industry there wasn't any testing either.
if you used cannabis and got caught, you'll have a police record for up to 5 years
when applying expect it not to be in your favour