For me, SPDs were about looking after my knees.
Riding flats, my feet tended to never be in the right place which for trail/ Park riding was never an issue. Short sections with a bit of a climb in between, it wasn't an issue.
Riding longer distance and spending longer in the saddle meant that bad habits of having misplaced feet caused issues with my knees. Uninteresting things to do with tendons, muscles and ligaments meant that my knee was twisting on each pedal stroke which over 40 odd miles, caused problems.
SPDs meant that (eventually, once they were set up) my feet were always in the right place which kept my knees happy.
Depending on what/ where/ how you ride, SPDs (or others) will be beneficial on an ebike as you'll likely be spending more time in the saddle, more time pedalling and probably, more time rested while you pedal.
I never had issues clipping in/ out, I never feel like being clipped in is detrimental to my riding. Occasionally, it can make getting started on stepp techy stuff a bit difficult but the other 90% of the time, I don't see any downside.
It can be difficult to find shoes that fit properly and it takes a while to get your cleat position sorted but neither of those should put you off if you're up for a bit of fiddling.