I don't doubt that green size may have some small correlation one way or the other with pace of play, but I can't fathom that it's one of the top ten factors and there's a whole lot of speculation about it in this thread without much in the way of real data or even actual real-life observation.
In the meantime, I think the idea of smaller and severe targets as a way to challenge good players without stretching beyond 8000 yards has real merit, and it's bizarre to me that every trend in design for, like, 100+ years has mostly been toward bigger and bigger greens, with an occasional outlier like Harbour Town.
I mean, what do we even call a small green anymore? It feels like something around 7000 sq ft is probably about average on new courses of note. Maybe bigger even. Doesn't Pebble average closer to 4000? I have a hard time understanding how, in spite of some very popular-with-the-people courses like Harbour Town and Pebble Beach, it still just seems like there's never been a real trend of emulating their exacting target sizes.
If nothing else, smaller greens mean fewer flat areas to put pins. If Pebble's greens were 8000 square feet, missing short-sided and pitching with the green's tilt might just look a lot like it does on most Tour setups, where slopes tend to flatten out before a ball gets to the pin so that the out-of-position pitch isn't as hard as it might be if the slope fed right to the pin, and only the deftest of shots would stop within a few feet of rolling past. Pebble's greens don't leave room for such a player-friendly setup. They're too small, generally with tilt throughout, and don't always give the option of tucking the pin right in the middle of a nice flat 10' radius that any pro can hit and bury putts from within.
If the trend is going to be ongoing wussification of setups, small greens with tilt throughout are probably a little more setup-proof when it comes to still requiring strong players to think about their misses.