Depending on your state law and which particular officer friendly wants to stop you, ebikes may or may not be considered 'motor vehicles.'
I happily ignore all signs like that because Wisconsin has laws that differentiate 'motor vehicle', 'motorcycle', 'moped' and 'motorized bicycle' with 'motorized bicycle' added within the last few years. They haven't yet been updated to say 'No Motorized Bicycles', no one really rides them around here. Most cops probably don't know the newer laws either, so I'm waiting to have that conversation... In the meantime I just try to stay stealth by being not too obvious, being courteous on the bike path, faux pedaling, coasting unpowered and real pedaling around crowded areas. Sometimes I get off and walk it on the sidewalk.
Another tip if you get into trouble is that the specifications for posting road signs and markers is defined in code and statutes and it can be easy to win in court based on the fact that whatever sign was there wasn't a legal by-the-books sign. Watch out for any of those 'No MotorIZED Vehicles' signs, which could very will apply to you.