Rewatched the video of the static fire. I think I probably overstated a little, and honestly I think it may have been the lighting playing a trick on me to an extent.
Here's the engines during the first gimballing test when the fire broke out. Engine in question is far right and you can see some orange flame.
Several seconds later, just after the gimbal test stopped:
They all look pretty good here. So maybe not as bad as I first thought. I'm gonna say if it was running fuel rich, it wasn't outside of acceptable boundaries for flight. Again, this is NASA we're talking about, they'd have shut down if it had been unacceptable (unlike SpaceX...what's that? Software too conservative? Just a sec...).