I'm not sure about the specific statistics, however based on my experience, and I believe many other anglers have found this, when fishing artificial like chironomids, wet or dry flies, spoons, spinners, twitching jigs, 6 inch pink worms or beads set 1.5-2 inches above the hook, I have rarely experienced a deep hook set (I'm not saying never, just that it is rare and I acknowledge that it may also depend on angler experience etc.). In the past when I fished with roe or an occasionally real worm, the chances of a tongue or deep throat hook set seemed to go up dramatically; certainly enough that I noticed the difference and now very rarely use bait. I now also use the trailing hook method on spoons to try and minimize deep hook sets and from my N=1 experience, this has been a worthwhile technique. Therefore, the theory/conjecture that roe and other real baits result in increased mortality due to increased risk of deep hook sets and increased risk of blood loss appears to be both logical and reasonable to me and also fits my experience. The fact that it is banned by regulatory authorities (with a lot more experience and access to research than I) in many (most?) non meat fisheries provides additional credence to this theory.
I'm not sure why discussions on the potential merits of banning roe or other real baits generates such angst. Everyone would be on a level playing field and good, experienced anglers would still catch plenty of fish.