Thank you, Basj - that seemed to do the trick. (And incidentally I tested this on Word after my original post earlier today, and I had the same experience there. Perhaps it's all Office products.)
Somehow I missed that "application exclusions" button altogether. That would probably be my last resort, as in most cases I would like to at least preserve the option to group like windows together. I just would prefer not to have to be forced to ungroup them.
Am I correct in assuming that the "never automatically group" option is supposed to limit them from automatically grouping at first, but still gives me the option to do so if I choose? And that it apparently isn't working properly in this narrow instance?
Thanks for the quick responses today, everyone.
