Huh? Why should WC1 have that?
Because it came from WC1, it's the first few notes of the WC1 theme that I mean. The segment also returns in the Wing2 intro music.

Probably to suit digital audio they would have to redo it anyway, so why not do it from scratch. Also Sega-CD had it's own PCM soundformat running through some weird customized hardware(It's a lot more then just a CD-player expansion!)

Also in those days I was one of the few who had access to a roland-compatible soundcard, whereas the majority of players were stuck with an FM-synthesis based card, and few had heard the original WCsoundrack as it was intended anyway.