not convinced he really knows what shutter lag is!
Shutter lag for us photo-heads is when you press the shutter and the image is captured a short time (hopefully) later. There's always a lag and the only question is how long that lag is.
That lag is usually tested on the first shot with no other shots waiting to be written to the drive from memory.
Then you have time to next shot which is how long the camera/phone takes to empty the data from the last shot onto the drive and make itself ready for the next shot. You can nearly always produce a larger delay here depending how many times you press the shutter and how much data each photo represents.
What he's shown there is a blurry photo of a constantly moving item and that's not really shutter lag in my book, that's shutter speed. Simply the shutter speed hasn't been set fast enough to grab an image without getting motion blur. Of course, you can say THAT'S a negative, but that's not shutter lag to me!
in the dslr world, if we're going to be looking for a great shot of something constantly moving, with 4k and wow 8k video, I'd be swapping it to video mode and grabbing a frame out of that, there should be easily enough data... or just going pro raw and setting a higher shutter speed.