I think the comment you referred to didn't suggest relying on some indication of upcoming action from the subject to start holding the shutter down. Instead it was about using a variantion of the EOS M6 II pre burst feature (also present on many non-Canon cameras, of course) where the camera continuesly stores images from the sensor in the buffer, but doesn't write them to the card - until the button is pressed, in which case the images from the last second before the button press are saved. So you don't have to rely on any indications, and instead only make a camera input once the action is over.you may not have much if any warning of when the interesting moment is likely to happen so taking bursts may not be the answer
It‘s basically turning a mirrorless weakness - each image has to go through the processing pipeline before being displayed - into a strength. Because while a EVF can't have 0 latency, it can temporarily store the images it displays, while an OVF has no latency past the speed of light, but as there are no images involved there's nothing to store.
As of right now, the discrepancy is pretty huge though. The 1DX III goes from 2850 shots per charge in the OVF (That's CIPA, not real world usage) to 610 in LiveView. And that's despite the massive improvement in efficiency that allows it to take twice as many shots as the 1DX II. Granted, LiveView does not equal an EVF, but the point is battery technology improves at a tiny rate at best, and the current gen DSLR (90D & 1DX III) saw big improvements in efficiency, I wonder how well optimized they are already.battery life may (or may not) cease to be a practical issue, ie even if a DSLR would go for longer on a single battery, a mirrorless camera may last long enough
The point of course still remains that as things improve, it comes down to the individual if the advantages of one system are big enough over another one to matter.