But going a level deeper, the whole position only exists because a company wants to get some job done. Describing it is just a means to achieve that. Not a thing in itself. I think we're circling about what I consider being the main point: What matters is if a job get's done. If you do it with a description and it gets the job done, it gets the job done. If you manage to go without and it also gets the job done, it also gets the job done. If you manage people by people and that gets the job done or if AI does it and also gets the job done... Delivering some goods is how a company makes profit. They don't really care how it's done because that's not what it's about. It just needs to fulfill a few criteria. Be profitable (have a good price/performance ratio) and be sustainable/reliable... It doesn't matter to them if it's AI, a human, with a description or without...
And I already had jobs where there wasn't any proper job description (just something on the paper). That usually leads to severe issues if there is any dispute. But nonetheless it worked out well for me and my employer. I know people who are in similar situations. Or had their job descriptions updated because things changed. So I don't welcome that as it will result in issues. And it shouldn't be like that. But speaking from experience, a job can be done without a description if circumstances are right. I also regularly see people organize their old stuff when retiring, read their old job description from decades ago for fun and that's not really what they've been doing the last 20 years.
I think our fundamental disagreement is, you say it's currently usually done like this and therefore that's the only way to do it. That might be a conservative perspective. But by logic, that doesn't follow. Just because something works some way, that doesn't exclude there being other possibilities or ways to achieve the same thing.