Does anyone know what the deal was with this spiral bound version? Was it part of a batch sent out to people to look for typo's, etc?

It definitely wouldn't be an editing copy. Pre-pub copies in general don't have any art. Covers would be plain, with any decoration being limited to simple things such as as box surrounding the title, and possibly the title being in its correct font.

I bet the original owner did something similar to what's described here on Reddit...

I got my PHB spiral bound at a local print and copy place. I'm pretty happy with the way it turned out!

misterspock wrote in AD&D 2e spiral bound PHB question:...if the pages were removed from a normal book, wouldn't there be some residue?

If the original owner brought the book to a place like Staples to be rebound, the spine would have been cut off with a paper cutter, leaving no residue. This applies regardless of whether the book was to be spiral bound, comb bound, or tape bound. The only way they wouldn't do that is if the book was already disassembled AND you requested they not trim the edge of the paper.