I agree. I think it also helped him become better on the ball, playing in those tight spaces and having to pick his passes quicker and under pressure. His RB performances were very up and down, but I imagine the experience helped in that respect. He always looked a great defender when he first joined, but early on he looked like he'd never been in possession of a football in his life. His passing still isn't brilliant, but it's infinitely better than it once was. His touch and dribbling is much better too.
I'd like to see him as a #6. From his performance today, he was great, but he is attracted to the ball and always wants to be where ever the ball is, which a centre back just can't do. A defensive, ball winning midfielder would have a bit more freedom to close down opponents and make tackles higher up the pitch or out wide whilst not leaving gaps in the back four.