Yeah not sure that's a large enough sample size. 16-17 and 17-18 were both ninas, 18-19 at least brought most in the area to climo with the Dec and Jan storms, and of course 19-20 was a torchfest. That just seems like a random mixed bag, we've certainly had multiple instances of that within even the 21st century, a good bit in the 80s/90s too. Considering how much of a distinct lack of sustained blocking we've had since 10-11 I'd say that maybe that was when the flip was switched, but what do I know I guess.