I get how it can be useful, but when editing files, it was easy to locate and open the PDNs to work on, then save them to the same folder with the finished DDS/TGA files, but when going to open the finished one, it can become hard to differentiate between which is the PDN or the finished file, I can only really tell via small changes between the preview or the filesize at that point. Everything else about them is nearly the same.
Meanwhile, with it having the simple thumbnail image: https://gyazo.com/0719b893c0b8e19675d30fd6b1342016
Comparing that to the PDN preview, it makes it easy to know which is which, you know?
I do prefer that to be the case, than more or less having to guess out of two files.
I wouldn't mind that being a feature later on.
Hope this helps!