Interesting article. I've not seen issues with the rolling shutter yet, but perhaps the little owls don't move bits quickly enough to see it, and the hobbies were too far off to be affected. I noted the other day when a police helicopter was flying around behind my house, and I took some shots with the electronic shutter, the rotor blades were fine, but it was a big crop, so it must only manifest itself when the subject is a frame-filler, which figures, from my understanding of the issue.
The wake-up time is a bit of an issue, but I've already started to work around it, by compensating for the time it takes to come back to life, by pressing buttons on it before it's anywhere near my head, so it has activated by the time I am looking through it.
As far as I know, the viewfinder in the R5 is of a higher resolution to that of the R6, so perhaps that explains one of the issues he mentions in that review. The R5 also has a mode whereby the viewfinder can run at a faster refresh rate (uses more power) so fast-moving objects appear more smoothly.
Sadly lacking in hummingbirds here in the Midlands to test it on. Not lacking in rain at the moment alas...