I am impressed that you were able to shoot swallows in flight! I know how challenging they can be. I suspect this means that the viewfinder must not black out nor delay very much, if any at all.
When I tried to shoot wildlife with an EOS R through the viewfinder, I found tracking birds in flight very difficult due to blackout and delay which would cause me to lose the bird in flight, and with long glass, like 800mm, once you lose your bird it can take several seconds to reaquire in the viewfinder, if you haven't lost it entirely. A very different experience than shooting through the viewfinder of a 1DX or 1DX Mk II, where I very rarely ever lose a bird in flight, even 25 minutes after sunset.....
I like the EOS R for shooting landscapes and people, but never used it very much for wildlife because of the delays and black outs in the viewfinder.. So I am indeed looking forward to the R5.
My next question is your experience dealing with 45 Mpxl files - not the data so much, I am certain it is lovely, but how your computer and LR react to the much larger data flow required.