Non-developer here but I might have some insight on general hiring practices: First of all, most companies, startups especially, are really bad at training. Like, really really bad. A majority don’t have any kind of formal training programs until they hit 100+ employees, and even then the training you get is usually created by HR and lacks any kind of technical depth. It’s hard enough to even wrap your head around the basics of how most tech companies are built as an early employee; trying to turn that complexity into a simple training program for new hires is hard and people rarely have the time or resources to do it well.

That being said, if a company is preparing for growth they need to plan and document for those trainings ahead of time, and they’re probably better off hiring fast and teaching quickly on the job. Not documenting how your company works is another kind of technical debt if you think about it, and a lot of startups scramble to make up for it when they find they need to hire quickly but those hires aren’t getting up to speed as quickly as they should be. So they overreact and think it’s the quality of the developers that’s the problem when it’s really their own lackluster training resources causing the issue. Also, the company I’m at just constantly maintains listings for front end and back end engineers and data science just to try and keep a constant pipeline coming, but the actual needs and experience levels they’re looking for at any one time on those teams do change. IMO you should never apply to a job post that’s been up for 1+ month; always target newly published listings and you’ll up the chances a recruiter reaches out. The rest is just HR noise.