That's not the science, science is they were all in the same zone, well except for gravel guy lol.
I could post half a dozen mtb vs emtb vids. Everyone comes incredibly close to heart rate zones. Only difference is calories burned. There are pros who swear that training on an ebike is more efficient to their training.
I'm not here to preach, only share the deep dive I'm in right now. I'm also not giving up my hardtail but possibly replacing my ripmo. I am guinea pigging this as a life long laborour my body is breaking down. I want to still get up daily to ride and still go to work. Again most people that have a negative attitude have no idea and for the that fact neither do I yet.