Quite so. That's why I keep saying good quality strop leather rather than just vegetable tanned cowhide. The difference is primarily in the way the leather is worked, i.e. boned. And horsehide will produce a better strap than cowhide because of the higher levels of silicates, BUT..... that's only if it's been properly worked! T'aint just one, but all together!
Of course, if one were to take vegetable tanned cow shoulder or butt leather and bone it for about 10 hours it would make a better strop than horsehide that wasn't boned! In lieu of spending 10 hours, one can case the leather and roll it with a heavy rolling pin for an hour or two, but this isn't nearly as good as boning. (I like to use "Pro-Carve" for casing leather, but a mix of windshield washer fluid and water work pretty well too.)
I want him to strop it but I would feel better if his strop had diamond compound on it
Here's an idea... How about (and I'm assuming you don't wear a beard) you go to a barber with YOUR strop with the finest diamond compound on it, ask the barber to first strop his razor with his strop and shave one side of your face, then have him strop with your compounded strop and shave the other side. Then YOU can tell us which you actually felt was better! No third party. No debate It's your face so only you will be able to tell.
I wear a full beard otherwise I'd give this a try. Absolutely subjective, but so is life! If you tell us that you found the diamond sprayed strop shaved better, I'll go along with that as fact and advocate the use of diamond compound. We have people here who are on both sides of the equation, each touting our own beliefs. Let's put them to a test. I think we can trust you to be honest with your results.
Stitchawl