Anyone can get a 2:i, if they wanted to. And anyone without an adequate social life can get a 1st. If you have a 2:i or higher, does that mean you’re automatically eligible to do PhD? No, of course it doesn’t. Doing a PhD is nothing like doing a BSc. You have to demonstrate (at the interview, or in your written application) that you can think independently, not regurgitate what you were taught at BSc level. There’s a difference, and if you can’t see it, you shouldn’t get a PhD.