LG, I agree the "mirror" scenario you suggested seems the most likely outcome now.
The NYA and SPX both sport the "mirror" look. The NDX/COMP have modified mirrors.
I had kind of doubted it because a different mirror was in play on the way up, and I've never morphed from one mirror to another like this. However, I can't see a better outcome.
Come to think of it, I was working off that read originally in March, but discarded it when the momentum started to stall in the 800 range on the SPX.