Maybe so.
Another theory is that swifty hasn’t improved or worsened since vanilla and that his skill level has remained the exact same. It’s just that the average player has gotten significantly better over the years and the pool of players that swifty was “better than” has diminished over time.
(for the record, I think Swifty is an awesome guy and I catch his streams from time to time. I just love his positive energy. I didn’t want it perceived I’m a swifty hater.)