Looks like the update did bring some improvement. It looks like previously the CPU would aggressively try to hit max turbo clocks (4.3 GHz for all core), overheat, throttle back (sometimes well below even base clock), cool down a bit, and then repeat. So the frequency was bouncing all over the place. With the update it seems to more intelligently target a boost clock that's more or less sustainable (~4.0 GHz). It seems like this improved overall performance, in addition to making it more consistent.
https://www.cnet.com/news/apple-macbook-pro-speed-throttling-patch-tested/
https://www.macworld.com/article/3292640/macbook/macos-update-fixes-macbook-pro-throttling.html
Hopefully there will be some more comprehensive investigation (I'm still curious to see if fan speed/noise changed).