Josie,
thanks for the detailed answer!
So it seems my question was just out of date.
Because I can see now that in the *latest* binary distribution, indeed a full commented bitcoin.conf is right there at the top level of the directory tree.
It wasn't there in v0.21 but it is there in v24+ so it must have changed in between.
So what we have now is exactly how I expected it to be.
I agree that auto-generation from a website isn't great.