Both Karma Chameleon and Pictures of Matchstick Men are DIY stemmed (though with the poor audio quality of the latter song itself, it's barely noticeable).
Not exactly a huge shock. Any time a huge hit that's eluded music games for over a decade finally comes to Rock Band these days, I never have my hopes up for pristine stems (i.e. Karma Chameleon, Black Betty, Breakfast at Tiffany's, etc).
As for Pictures of Matchstick Men, the song's literally 50 years old. I'm just glad to be getting something different. I wish we'd get more classic stuff, and psychedelic rock is definitely a genre we're lacking in.
Also, both songs are pretty easy on instruments (except drums on Karma Chameleon, I guess). Hit moar notez; git gud, etc, etc. Then you don't have to worry about stems.
Also wanted to add, album covers like this Status Quo one are why we NEED big album art back like in RB2 and RB3. That's such a cool cover and you can barely tell what it even is shrunk way down like that. That's always been my biggest gripe with the RB4 interface. The album cover is as much of a piece of the art as the music is.