That's a familiar concept, that depth and intensity of sensation revealing what was real and what had been simulated. It went deeper for Themis, having felt what it was to not possess a physical body and the decrease in strength that caused. What Angeal speaks of, however, makes him think of somsething else entirely.

He continues working as he speaks. "Your increased senses are amongst your enhanced abilities, are they not? We have all been diminished in this place. Perhaps it is an extension of that, similar to a reduction in my physical strength or the depths of energy that I may wield."

It makes logical sense, at least. A dampener on everything, broad strokes rather than selective reduction.