Novelty use of a Queen excluder

Looking through one of my colonies today, when I opened up I was surprised, to put it mildly, to see the queen excluder on the top of the top super. This hive is brood + three supers. 

Eh?

Or course, the bees were totally happy, with brood spread in lovely solid swathes in all boxes except, of course, the brood box. 

From my point of view, it's a royal shambles! Why on earth did I put the QE on the top? She's a marked queen, everything is 100% normal... My notes are not much help, listing the hive as BS/E/SS, and a remark that at next trip I would consolidate to B/E/SSS. 

Was puting the QE on top senility, stupidity, or incompetence?

(Don't answer that!)

Here's an old photo of the colony before muggins went crazy...