Plenty of traditional bikers are folks who are using bike shares and do things like not wear helmets, ignore road signs, ride two abreast, and swerve without warning. Also a problem are the "pro" bikers (you know, the ones on a racing bike, fully decked out in gear) that tend to ride ~10 mph faster than everyone else and pass aggressively.
E-bikers on the other hand, go in a straight line, usually single file, without swerving and seem to follow traffic signs because they have an easier time accelerating and decelerating.
Again, just my anecdotal experience -- I ride ~5 miles to/from work in New York.
I wouldn't be surprised if that overshadows any danger from introducing different travel patterns compared to regular bikes.