Thank you, C.LYDE101!
I thought maybe this was a completely obvious thing that only I didn’t know … the Ops Manual doesn’t even define “flatten” … but I guess it’s, based on your very helpful comments and the lack of others that maybe it’s not something that people know a lot about.
I haven’t been at the DAW for ages, but I will check out the effect of flatten vs. bounce on edit history.
Thanks again!