Konami SCC Games Sound Enhancement
Oh, and to address your last question - indeed, both Yie-Ar Kung-Fu games are 'small' (16kB and 32kB respectively) compared to Penguin Adventure, which is a MegaROM of 128kB.
Back then, a bunch of smaller games would easily fit on a Konami Game Collection disk and also in the RAM memories of most MSX models, whereas bigger games could have been a bit more problematic regarding ROM size. This may also have meant difficulties in adding (a sound driver for - and the mapping of) SCC support. When those collections were released, the SCC had only been 'invented' for about a year ago.
Also, Penguin Adventure has a pretty lenghty and diverse soundtrack compared to those earlier games, which makes it quite the endeavour to re-arrange it all to SCC. All of this ofcourse translates to time and manpower, which means money.
So there could have been multiple reasons for Konami not doing it, actually. 
[EDIT: The only title that defeats the points that I made is Gradius, which also is a 128kB MegaROM and did actually get an overhaul on Konami GC]
