Yes. But...
I keep wondering about the TENS OF MILLIONS of AR15 rifles since the 1970's that only get commercial factory ammo, which don't have milspec primers. Why aren't they all blowing up and slam firing? Surely there would be more than the few on YouTube and the anecdotes you hear on Al Gore's Internet.
Using milspec primers in rifles with floating firing pin is good conservative and safe advice for those of us who wish to be extra safe and conservative. Maybe it's not a bad idea to minimize disaster to such a small margin that it just never happens to you. Sounds like reasonable advice to me. It's all personal choice. If you wish to be extra safe, there are extra things you can do. It is good to have a choice.
Just for kicks, 8 years ago when there was a post-Obama run on primers and they were hard to find, I decided to do an experiment. I took a box of 1000 small pistol primers and loaded max loads of H335 in mixed 223 and 5.56 brass. Yes, that was small Pistol. Not small rifle. I inspected for dimples in the primer cups, and there were a few. No different than rifle primers. All pistol primers fired perfectly, not a hint of a problem. So I did it 4 more times for a total of 5,000 rounds. Not a hint of a problem. If the dangers are ubiquitous, you would think there would be at least a tiny hint of a problem in 5,000 rounds, at least once. 5,000 rounds is not lock solid conclusive, but it is interesting evidence. The potential problems may be smaller than Al Gore's Internet tells us.
Can slam fire occur? Theoretically it might, especially in a marginal rifle with marginal ammunition. Keep your rifle tip-top shape and load your ammunition correctly, you minimize the "might" to such a tiny margin that it just never happens to you.