I was looking closer at an OpenType 'zero' feature for the slashed zero replacement and realized it was written out using each grouping bracketed rather than having each separate grouping designated as a class.
sub [zero zero.op zero.lt] by [slashzero slashzero.op zeroslash.lt]
as opposed to
sub @zero1 by @zero2
I was just curious about this as it all gets decompiled so is it simply a case of the feature being easy enough to write out vs. using classes?