By that, I mean that if Preserve Layer Name = False, then a single-layer EXR will have these channels:
And if Preserve Layer Name = True, then the single-layer EXR will have channels like this (that include the “layer name”):
Channel names like “Arnold_Direct_Diffuse.R” can cause problems with some software, so by default Preserve Layer Names is set to False.
Note that Preseve Layer Names applies to single-layer EXRs only. If you’re writing out multi-layer EXRs, you’ll always get names like “Arnold_Direct_Diffuse.R”.