E-bike calorie burn too high

I use both e-bike and normal bikes. Usually mountain biking. I have done the same rides on both bikes. The Strava effort score was 50 e-bike 145 normal bike. So Strava is seeing a lot more effort on the normal bike. However calorie burn was 1,200 e-bike, 1,500 normal bike on my Garmin readings. Strava is reading my Garmin but clearly interpretation is different. I don't like the new 'workout benefit' it doesn't give a score so seems quite vague. I feel like I am putting in a lot less effort on the e-bike. Especially as I am riding with friends so I can't use the e-bike to its full potential. I think that Garmin is vastly over estimating my calories on the e-bike. My HR average yesterday was 90 v 125 on a normal bike and maximum HR differed greatly as well. I use a 530 Edge or a Vivoactive 5. Any thoughts?