The 3 at the back discourse stems way way back. English players don't understand 3 at the back football, it's all about the 4, anything else is a disaster.
Steve McLaren wanted to play 3 at the back for England and did. He sent the team sheet up, ITV lined it up as a 3-6-1 or whatever it was at the time and then spent every minute of pundit time criticising the foreign concept that is the 3.
It's why 9 times out of 10 whenever you see a team sheet it's a 4-3-3 or a 4-5-1. You even see it with City sometimes where they will put down a safe formation but then they get on the pitch and the commentator will say so and so actually seems to be playing in Midfield or whatever.
For whatever reason, old hats associate 3 at the back as a back 5, and even worse so that knowledge becomes generational despite the fact that a lot of teams build with 3 at the back in modern football. Southgate has not modernised that opinion either.