Tbh i have a feeling that the 30fps will be much more of a marketing gimmick than a practical tool for a while, mainly because of the lenses, or the focusing motors in lenses to be more precise.
If you look at the R5/R6 manual you'll see several lists, one for EF and one for RF glass, listing their support of high frame rates. given that most relevant EF glass peaks out at 12 fps, only several RF lenses currently support 20 fps, and even that, only wide open and only above certain battery charge levels (i'm assuming this is related to output voltage). On top of that - given that you cant really use teleconverters on RF 70-200's, or lack any telephotos except the 100-500 zoom, and have no 300, 400, 500, 600, 800 L primes coming anytime soon professional sports/wildlife/action photographers will have quite a useless 30fps spec on their 7k$ cameras.