I guess my concern is that yes a MTB is as fast uphill as a riders legs can push them. However an EMTB is as fast as the riders legs plus the motor can push them. We now have a situation that uphill riders are able to go significant speeds, with their heads down, into other trail users.
On the flat normal people with normal people skills are able to go faster than Olympic athletes: https://youtu.be/2NkMrgoCIiE?t=780
Even downhill they are quicker. https://www.youtube.com/watch?v=AF97lV798iM
To my comment "lacking merit", I ride with someone who got an EMTB because he is getting older and he felt he needed it. Unfortunately this led to an injury with uphill speed being the cause. He is lucky to have made a recovery but as people get older adding speed to an already dangerous sport can lead to injuries that could have otherwise been avoided. Ironically instead of extending their riding years they are sidelined if they can't make a recovery.