Yeah, I read the same info on Nexus re:Distant DetailHF, but despite looking and looking, I could not find any info about whether it was safe to clean anyway. I have reproduced the same effect with other mods since, Expanded Apocrathy Inventory being 1, it behaved the same way when I cleaned it. It was reporting 1 UDR and when cleaned it "cleaned" more than just the 1 UDR and then flagged with an X, I had to hide the Esp file in order to reinstall it as well.
I really just wanted to potentially warn others that cleaning these 2 mods can cause problems. One thing I did fail to mention, and it was pretty major, but I am not going to do it twice to see if it can be reproduced, it crashed MO at one stage when I was trying to isolate the CTD cause, and then I had to reinstall all my mods from scratch, luckily I kept all the downloaded zip/rar files, it was still a hassle though and one I have no intention of repeating any time soon.