Well lets discuss the options with pros/cons shall we....You started it
Perhaps we should make the title, "How to make your ebike more comfortable and the front end wash out more"
Raising your handlebars with a stem riser causes quite a weight shift towards the rear. This will manifest itself as less front end grip on offroad level and uphill terrain. When Im really cookin offroad on my ebikes, Im usually limited by front end grip so rising my handlebars is the last thing I want to do (especially 75mm). I reluctantly had to raise the bars on all my bikes 1inch this year due to hand pain and immediately noticed reduced front end grip. I now have to beware of this and purposely lean forward more at times. I went thru quite a 6 month process (grips/handlebar rise/stems/handlebar clocking) and learned alot in the process. Note that I also use a bigger tire in the front for more grip almost always.
In addition to that, raising your bars might actually make it worse although this would be a limited case. When I first got my Bulls Evo eMTB, I had hand pain. Ironically flipping the stem over so it was -6 degree and rearranging the headset spacers to lower the stem worked 'in this case'.
Basically there are two issues causing hand pain.
Weight on your hands
Weight distribution on you hands
Weight on you hands can easily be reduced by shortening the reach to the bars (making stem shorter, more handlebar sweep depending on handlebar design) or raising the bars (higher rise stem, riser bar or stem riser). Note that this also changes the weight on your front wheel. No free lunch here.
You can also move the seat forwards which will have the added benefit of adding weight to the front end. Maybe your bike has a setback seatpost that you could change out.
Weight distribution on your hands can be changed with grips, handlebar sweep (up and back), handlebar clocking (rotating bar in styem) and gloves. You could also try different grip position or something like togs(
https://togs.com/) which I use on my acoustic FS mountain bike.
Handlebar width also has effects on both the weight and its distribution.
An then there is core strength. Perhaps the cyclist just needs to do more situps.
Bike fitting can be quite a process and many time non-intuitive (I recommend watching Bike Fit Adviser on youtube, I dont agree with all he does but its a good source of info).
Im guessing using a stem riser works for alot of newer riders (nothing wrong with being a newer rider) as they arnt pushing the front end much (if ever).
Here is a good stem calculator
, look nothing like mine.
(I have received many complements and imitators.)
