When I came to this forum I had been living with, and very aware, of OCD for over 25 years. I had never heard of HOCD, POCD and TOCD. It didn't take me long to understand what was happening because they all act like, and ARE OCD. H/T/P OCD are not given as a clinical diagnosis, OCD is.
Even though I haven't looked into it, I think it is safe to assume these things are relatively new. In fact I wouldn't be surprised if they came about, and were given a name, by the people who have been suffering these themes, and then adopted into the culture of OCD when word spread.
More to the point, I have had fifty-plus OCD themes/fears/flavors, etc that appear no where and are probably unique to me. In fact, before I came to this forum, I thought I was alone in some of the "weirder" ones. But after I became a mod, some members would PM me and tell me some of their, what they thought, odder "obsessions" because they were too embarrassed to post them publicly.
It was then that I found someone else who was also having the same unique "What ifs..." as I was. I was shocked.
Obsessive OCD thoughts are a placeholder for ANYTHING you can think of - and if you don't find a lot of your "fears" online or anywhere else, you are no closer to your fear being the truth.
Otter.