Rolling Shutter and Shutter Speed / Is there a comparison

[Kayaker72]

You mentioned 1/500th of a second, 1/60th and 180th of second. Do we know how fast the electronic shutter actually loads and clears the sensor?

The 1/60th and 1/180th of a second is ballpark what I have heard people estimate as the readout speed when using electronic shutter for the R5 and R3. For the R3, here is DPReview estimating it at just under 1/200th of a second.
https://youtu.be/oYFLrRj8ODE?t=854

The part of this that is confusing is that we know from HSS requirements for the flash that for a shutter speed over 1/250s, the shutter open and shutter close overlap. You need multiple rapid flashes to illuminate the subject while the two shutter curtain moves and different parts of the sensor are receiving light... which means any shutter speed over 1/250s technically should have the same rolling shutter effect. With flash and low ambient light you might even expect to get multiple distinct chunks for each flash exposure as opposed to the continuous jello look you get from slow readout.

I'm not invested enough to bother doing any experiments though, and a quick google search didn't reveal anything interesting. All the links talking about shutter curtains are about 2nd curtain sync flash timing to get trails, not anyone talking about artifacts.

You are not wrong.

It seems electronic shutter disables flash options in the R5. I am traveling right now without my R5 so I cannot verify, but per R5 manual page 165 "In flash photography set (shutter mode) to option other than Electronic." Page 174 flash sync speeds are 1/250th for Electronic first curtain and 1/200th for mechanical. And, if you need more, Page 249: "Precautions when set to (Electronic):...AEB and flash photography are not available"