When you can’t get good PNP transistors. Or just have NPNs. It’s possible that only the PNPs are fake, or that the NPN fakes are stronger. If fake, they may not be complementary types inside.
To me it is suspicious that they were using the old Fairchild logo on the more recent lead-free finish (dull, etched look as opposed to shiny lead-tin plating). When the MANDATORY switch to lead free happened, it was after ON bought Fairchild. New packages with that particular finish would have been labeled “ON”. The ones I have with the old F on them still had the lead-tin plating on the leads. That’s how long I’ve been working from a batch of TIP41/2.
Some feel the Quasi can turn in a better subjective performance. It has a different (and always worse in pure numbers) distortion profile but it has a good reputation for sonics.