Import email mailbox without putting individual items in groups

So I’ve got a pile of emails I want to import to DT and I’ve run a few pilots to see how things work out in practice. It’s not clear to me why the import for “Add Mailboxes & Attachments” places every individual email item inside a group. The downside of this is that it wrecks the folder hierarchy I have set up with emails which is now quite cluttered and nearly impossible to navigate given all the items within those folders that now sit alongside a pile of single items in groups. Is there some way to disable this behaviour? I can see how the import for “Add Messages…” doesn’t have this behaviour, but I’ve got quite a lot of folders and don’t have an easy way to replicate the hierarchy with that method…