I don't think that holds. Internal docs for bespoke frameworks, with examples, are effective at steering AI. The main thing is that both the API and the docs are well written. Easier said than done, but you can ask AI how to write effective documentation for AI.

>if company uses a very well tech stack, development and rewrites will be faster due to AI having way more examples to draw from.

Eh maybe not.

Stuff that has a lot of deprecated features is honestly burdensome on AI. It keeps rediscovering the deprecated features as the understanding that they are deprecated fall outside of the context window.

What you need is something that either never deprecates syntax, or is <10 years old with minimal changes over that time.