I also tried submitting what I believe to be a bug so I guess I'll place it here as well in hopes the devs find it.
After disabling timestamps, When I create a new chat tab/window, the timestamps show in that new window, although it's disabled. The timestamps are not showing in the primary tab/window, just the new one I created. Looking at the addon settings, there doesn't seem to be a mechanic for splitting timestamp settings across windows, so I'm assuming it's a bug.
To be clear, "Chat Timestamps" is set to none in the stock interface settings.
Thanks for your time!