I'm confused (and an electricity layman, so please excuse), but why would that power requirement of NFC matter in conjunction with the eInk power usage? Why can't the NFC reader be isolated from the display's power usage?
The devices for updatable price labels based on eInk already exists and I mention it in my post, it's powered by a low self discharge battery. Those IIRC use a special radio fob that connects to your phone instead of using NFC but you could probably do a largely drop in replacement for the radio circuit with NFC but that still doesn't solve the issue of updating the eInk screen. That's an order of magnitude more power required.
It's extremely obvious the person you replied to was talking about controlling the tablet, not supplying electricity to it. Their subsequent remarks are beside the point, this is what led to the confusion in this thread.
So yes, of course NFC can be isolated from the displays power usage, the originator of this thread was just suggesting it would be neat if you could power it via NFC.
But NFC doesn't provide nearly enough power, nor likely enough bandwidth to do that in a reasonable amount of time.