Okay,
now I understand what you're describing, have been able to duplicate the problem, and I believe it IS a bug. What's more, I also think it's worse than what you said, because playback
does actually start at the beginning of the loop - but the play cursor in the loop seems to start wherever it feels like starting.
However, I also understand why I wasn't having this problem. This is because I almost always edit the Loop in context with other tracks, so I have a different workflow that doesn't reveal this problem. So, I've been using a workaround without even knowing it. Here's the workaround until the bug is fixed:
1. After opening the LC, loop the clip in the Track View.
2. In the Track View, place the Now time wherever in the loop you want playback to begin in the LC (e.g., at the beginning).
3. Use the main transport controls to stop/start. Do not use the play button in the LC window.
Now it should work the way you want, assuming "On Stop, Rewind to Now Marker" is checked under Track View > Options. If you don't want to hear the other tracks, solo the track with the loop you're editing.