Yes, of course. 250W legal limit is set on motor rated power, which (with some simplification) is a label put on motor by manufacturer. Some manufacturers are more flexible and will put right label for some distributors (if asked nicely) and some won't. I love flexible approach to the subject by Grinn Technologies. You want legal label on? They will engrave it for you
Laser Engrave 250 Watt Continuous Power Rating on Motor Side Plate. ALL Hub Motors have an Operating Point (RPM and Allowable Temperature) where 250 W is Max Continuous Capability.
ebikes.ca
You would have to look really hard to find a bike restricted to 250W
View attachment 352276
Above you have road legal 250W rated motor. 48V x 15A = 750W. You can have legally all power you need within some reasoneable boundries of course.
PS Fragment you quoted was written by Flecc - our legal expert, but I see it now and I don't think he got it right. IMO it should be:
"250 watts maximum
motor rated power, 15.5 mph maximum assist speed and power only when pedalling"
I am going to write to him and ask him to correct his legal guide.