Perhaps a silly question since I haven't delved into OOB at all, but can't it simply be a way to efficiently use game assets? Areas usually consists of same-size squares, and this could just be a way to fill out an unused space. Sorry if I ruin someone's fantasies... 
I'm thinking this might be the case too. When dealing with things that the player may never see, they usually don't bother to put in such detail. Only areas that were scrapped mid-development and things walled off last minuet tend to have any significant detail, but everything else is either base textures or empty copy-pasted structures that are only there for the scenery. It is most likely their default 'active eluvian glass' asset that they decided to reuse.
But if it was intentional, I do have to wonder why he would bother to go back at all. The Inquisition and its allies have likely picked it clean by now, and it is very likely that the Sentinels have moved on ever since their purpose (protecting the Well of Sorrows) was taken from them. At this point in time, the Temple of Mythal is no better than any other ruin aside from a few tidbits that are of academic interest.