Are you talking about the “O” toggle? It seems to give me permanent red patches even if I just use Filmic RGB or Sigmoid. I even tried opening an EXR that is strictly clamped to [0.0, 1.0] range, and it would still give me large portion of red patches.
There should be clamping or equivalent operations in place in the AgX processing chain, this doesn’t quite make sense.
Anyways, it’s the visual result that matters, again, it’s forming an image, written with visual grammar. If you don’t see any banding or posterization or visual discontinuance where it should’ve been smooth, it’s all fine.
If the primaries tab is turned off, then it’s just a simple curve, and it’s not AgX anymore.