That's probably due to them being around for decades now. Most reviews and feedback tend to be on newer products, and the HMMWV and H1 weren't all that common, not to mention they were and still are expensive vehicles.
You're right that specifically finding reviews for HMMWV/H1 with 39.5" tires is pretty challenging.
Here are a few links to pictures I found
www.intercotire.com
This page does have discussion on interco tires on H1 in general, but figuring out exactly which tire is what takes more familiarity with them than I have
General thoughts after reading through a lot of it is they work fine and are designed for the weight, but you might want to get the paired 24 bolt rims if you're going to be driving a lot when really heavy (like over 12k lbs, as I believe your max load can be as high as 15,500 lbs in the M1165)
They are designed to be an off road tire. If you're going to be doing most of your driving on the road, then they aren't the quietest or nicest ride, but at least they will look cool?