As said in the article linked above - the normal legal UK ebikes don't really need a different tyre
The extra weight on an ebike - from the motor and battery - is really not that much compared to the possible weight differences between different riders
(I will not be mistaken for and Yates twin any time soon!!!)
SO that is not a concern
and as the legal motor cut off is 15.5. mph then , although the average speed of an ebike is probebly slightly higher than the rider would normally do - it is way lower than the bike might be doing witha decent tail wind or on a long downhill.
I base this on the fact that I an not really fit (at all!) and yet at times I cycle my legal ebike at 18-19 mph for several miles if the wind is right - and obviously a fit healthy and younger rider (and some older!) will be able to keep up with my ebike and me with no problems
Hence the speed ability of the bike has to be the same as for non ebikes
However, go up the scale a bit and you quickly get to the sort of things you sometime see delivery drivers (and others) use with suspiciously large hob motors and a suspiciously lack of pedalling at suspiciously high speeds for a bike!!
On those I would suspect that the tyre might need a better tyre compound to be able to cope with consistent higher speeds - and, more importantly, frequent stopping from that speed and with that extra weight!
So - in my opinion - ebike ready is probably a marketing thing mostly and someone with a legal ebike doesn;t need a one. But if it does say than then it is not something that should put you off - just check out the normal things like tyre weight, rolling resistance and puncture protection
