The "hearing the song first" is very easy to explain, but not easy to understand if you don't share the same attitude: I'm an extremely picky dancer, I only like to dance to the songs I "feel" (whatever it might mean). My taste is pretty much set and irreversible, so if I know from the start I won't enjoy a song I won't bother (in social setting, that is, but it's even more important for a project like this one)
Along the lines of what you're saying, I also know "what I like and what I don't like" -- but there's also an aspect of being in these compilations that you can you use to provide a new challenge and develop yourself as a dancer. From a personal standpoint, I wasn't in Compilation #1 because I was a little nervous about it, and, just like you, I wasn't in Compilation #2 because I didn't "feel" the musical choice (no offense, sweavo!

). I did feel the music for Compilation #3, so I participated. After that rewarding experience, I promised myself to participate as many times as possible in the future, as a way to test my skills and develop my musicality.
I suppose if you're completely satisfied with your current dance skills and don't have any room for improvement (just like there's no room for changing your musical tastes), then we won't convince you to dance to a song in the compilation that you wouldn't pick for social dancing. On the other hand, pushing yourself out of your comfort zone and thinking about the music in a new way has some value, I think. It's also educational to the rest of us (as observers) to see how other people interpret the music.
Like I said before, I didn't join Compilation #2 because I didn't have a feeling in advance for how I could interpret the music. But then the video came out and it was cool to see how the music could be interpreted in ways that I hadn't ever imagined -- although perhaps I
could have imagined them if I had forced myself to participate. I even liked the song better after I saw how people could dance to it.

So, I volunteered for #3. Then, because of the way the song/video needed to be edited in Compilation #3 (*cough*
to compensate for flakers *cough*), chrisk and I were actually dancing to the same portion of the song that was looped by the editor. However, because we interpreted that portion of the music in such vastly different ways, it wasn't until my third or fourth viewing of the video that I realized I was hearing a loop of the identical section of music! I thought it was a very cool example of how widely varied dancers' expressions of the same music can be, plus a fascinating lesson in how the way the song is
seen can actually affect how it's
heard. I originally thought I was hearing two different sections of the song, when I really wasn't.
On a final note, Compilation #5 was the most challenging for me, because it took me so long to figure out what to do as a dancer to accent what I was hearing in the music. But, I eventually came up with some ideas and a few people seemed to enjoy my final result. In retrospect, I think that kind of intensive creative process was extremely beneficial to me as a dancer, and could be very helpful for any other dancer....
if you believe you have room to grow.