Unable to dupe your results, Nat. Added clips always appended to the main track.
However, I did notice an oddity during the test...
I reloaded a project that had a single AVI clip, then instructed VP to add the same clip the sequence end.
It did, but the first eight seconds or so were missing. Added it to the sequence start. Same.
I cleared the timeline, and dragged the clip to track one. First 8 missing again. No way would it use the
full clip previously saved in this one-clip sequence. Didn't occur in another sequence w/different clips.