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Unusual wax moth encounter

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I opened a bag of bare frames today to do a count, and found it full of frass and cocooned larvae, but unlike anything I have previously seem with wax moth (see photos).

First of all, these frames had been scraped of old brood comb in the fall, ahead of this 2021 season. All that remained was some patches of wax along the sides and bottom of the frames. They have been stored in plastic compacter bags since then in an unheated shop. So, there wasn't much for them to eat - in fact, I had assumed that they would be of zero use to wax moths without any comb to eat.

The larvae were in brown cocoons covered with frass, rather than the usual white cocoons, but there was NO webbing anywhere. The cocoons sat or were loosely hung on the wood and the sides of the bag; there was NO burrowing into the wood, everything just brushed off easily. There was another bag of frames in the same condition right next to these, with no larvae. There were a few small holes (1/32-3/64" ca)in the lower part of the bag; these bags are very tough, and I check them for small holes or tears and tape them over. There were no similar holes in the other bag of frames. I have read that wax moths can eat plastic bag material, but then why just one bag? With all that, there was quite a lot of frass and detritus, given that there were only 7 pretty clean frames in the bag. The frames were very well cleaned of almost all available wax by these critters.

From what I have seen on line, it seems that both the lesser and greater wax moths look the same in regard to cocoons and webbing, the difference being the size of the larvae. Could these be some other kind of larvae?