My understanding there is no definition of “250 max continuous power”. It’s down to manufacturers intepretation of the law (until it’s challenged and a court clarifies it). I think they have intepreted it as meaning on the flat at max cutoff speed (15.5mph) the bike should consume no more than 250w, even if up a long hill the bike could consume more than 250w with no time limit.
If you look at the maths simplistically then
250W @ 60RPM is 40Nm
Most E-bikes work by some sort of multiplier on the torque the rider puts in, which is give or take a bit, concentrated around half the pedal cycle (the bit between 45 and 135deg after TDC), they don’t give you an added kick over TDC when torque is ~0. So ~80Nm which is what the “full fat” e-bikes have is probably not that far off 250W averaged over the pedal cycle. Obviously you can pedal quicker, but then maybe the machine gives less assistance, and bear in mind your own legs torque drops off with increasing RPM too.
I doubt there’s much gaming of the system going on in that case, and instantaneous peak of 500-750W at 90deg after TDC would sit within any sensible persons interpretation of “average” as it would appear to be done over a single pedal revolution.
Unless they’re being equally cheeky about the torque figures, but I doubt is as that’s car park bragging rights, if it was 85Nm average over a revolution and 200Nm peak, they’d be putting 200 on the marketing fluff.