It's not unheard of for small startups to have no training beyond "here's your email account and here's our repo". Sometimes you don't even get a company laptop.
It's not ideal but when everyone is swamped and pulling founders hours it's not exactly abnormal.
"Hit the ground running" is fairly common in startups as they don't have the resources to train.
I shortlisted a candidate once who clearly was an experienced developer, but because he didn't have any JavaScript experience, the CTO discarded his application. Very shortsighted but his argument was "We don't have time train people and JavaScript is a very popular language"
It's not ideal but when everyone is swamped and pulling founders hours it's not exactly abnormal.