In both sets of your photos.
I understand that the reason why many serious ebike riders use two fingers on the lever when braking is to keep more control on the handlebars.
Then your understanding is incorrect, as is the opinion of Jeremy.
You will actually find that "serious" mtb/eMTB riders, as you have put it, actually only use one finger braking. I'd imagine that no one other than Jeremy is using two finger braking.
As for control, two finger braking offers considerably less control than one finger braking, and a correct and proper brake set up, certainly doesn't require two fingered braking. If two fingered braking is required to control the speed or bike, then clearly there is an issue that needs resolving, be that with rider technique, bike set up, component spec, or all three.
Just one example, found within seconds of looking. The internet is rammed with reasons for one finger braking, but certainly not two finger braking. In fact I couldn't find a single UCI racing or down hill clip where two finger braking is shown. Edit.. looking again, I can't actually find any clip that shows two finger braking at any level or discipline of riding.
To end, if Jeremy thinks that one finger braking is "unnecessary" and that two finger braking is better, then perhaps you should be looking elsewhere for advice.
Why would you want less leverage and power.
Less modulation and feel.
Less control of the handlebar, with the associated risk that this brings.
Risk of trapping fingers, and so restricting brake lever movement.
More arm pump.
