More a nightmare than a dream. It lead to the terrible practice of tightly coupling frontend and backend code bases that led to inevitable pain. The language barrier between front/back-ends was a key aspect of web-dev that allowed it to a foothold vs. previous, unsuccessful attempts. Fortunately this practice hasn't taken over and sane architectures are still prevalent.

People do take into account the motivations behind what someone says and to me the motivations here seem different enough to make some difference here. The AI CEO has an obvious motivation to lie, but the person calling BS doesn't have such a clear motive...

I've used Postgres at a few places and the #1 problem was always high availability, not scaling. One Postgres cluster could easily handle 100000 transactions per minute, but when a primary node went down it was a page and manually failing over to the spare then manually replacing the spare. The manual tooling was very finicky but at least it worked, no automated solution came even close. Lack of a good HA story is why I avoid self-managed Postgres as much as possible.