You don’t need a masters in the UK. Three years bachelors and then straight into a PhD which is just research - no classes or teaching. And we produce more than our share of top science so it must work.
Then there's the program itself. DTCs (doctoral training centres) now mostly run 3 + 1 programmes, where your first year is a master's, involving taught classes and a research project. This is to get everyone up to speed on how to actually do independent research, and to build core skills. While it's true that teaching doesn't always form a mandatory part of a doctoral degree, working as a teaching assistant for at least one semester is often mandatory.
In short, you've mischaracterised doctoral education in England and Wales (Scotland may be different) to quite an extraordinary degree. I see no reason to comment upon the "more than our top share" claim, for reasons which are, I hope, obvious.
Well I'm not sure that many people without a first would seriously consider doing a PhD, so this isn't relevant in most cases.
> DTCs (doctoral training centres) now mostly run 3 + 1 programmes
Right, which is a big disadvantage of them. DTCs are just one way to do a PhD and they're not the traditional approach in the UK.
> In short, you've mischaracterised doctoral education in England and Wales
I don't agree! This matches from I see of students going into and coming out of the system today.