Does 15% more time to encode matter? How much time is spent encoding files vs decoding? That is probably still an negligible amount of compute, out of the total

Does 15% more time to encode matter? How much time is spent encoding files vs decoding? That is probably still an negligible amount of compute, out of the total compute spent on PNGs. Your specific number seem to come from an (old version of) an encoder that has super-optimized encode and not (yet) optimized CRC.