Good to know. I have a half-finished project I was going to snarkily call “Who’s Not Hiring” that parses through HN Who’s Hiring archives and lists the companies who post the same ad month after month despite the so-called robust hiring market.
I think you might be overestimating the consistency and reliability of how hiring is done. (For reference, I've worked as a hiring manager of software engineers for a few years.) I've seen departments just use the same description over and over for years, and share it between teams -- even when it's not even really correct at some point.
Practices vary wildly between company, and even between hiring managers.
You could scrape LinkedIn for people who had been at those orgs for a short bit of time. Frequent posts of the same job description + LinkedIn churn evidence = red flag.