I think this is true in the sense of there's no regulation it's just up to the developer, but my house (new build, 2021) has an RJ45 patch panel downstairs with 4 ports that lead to 4 areas of the house.
This was actually a surprise to me when I got the place because when I was speaking to the sales associates they had 0 clue what I was talking about when I enquired about network cabling. If I had known they were installing it as standard I'd have asked for more ports in more rooms, but hindsight...
But yeah, there's also 4 phone sockets as well, which I don't use. This solution might be interesting to try out, but phone sockets are in the same place as where the ethernet sockets are and I've no real need to expand in those rooms right now.