my understanding of dental decay is that it is bacteria which goes on to produce acids that causes the problem. Sucrose in table sugar (and much of the additives in food) allows development of bacteria and plaque. Manuka is known to have antibacterial properties which is why it was tested in leg ulcers all those years ago. So, if honey has antibacterial properties making it difficult or impossible for bacteria to grow, and bacteria cause cavities, then the logical leap is that honey doesn't have the same issues as other sugars. Just joining the dots here - I might be missing something though.

This is my understanding only and I could have the concept wrong so would be pleased if one of the dental professionals might explain this better.