You're right. I fought a tough fight, and I was losing all the way -- until today.
The problem in this case was that, with a Mac, exporting a .oml file did mean exporting the whole identity. Well, partway through today's chat with a Filipino Mac agent -- and they are, without a doubt, the best in the business. They bend over backwards to work with you and for you. With no exception, I have received no less than 110% effort and quality from them -- I had what my son-in-law would call a brain fart.
I was doing a transfer from an old 2011 Outlook to a new 2019 Outlook. As soon as I succeeded, I would trash the 2011, right? So I said, "Lets just trash everything except what I wanted to transfer." So I did, and created the .olm file of just the new stuff, and imported the file into the 2019 Outlook and it was all it took. Done. I didn't know whether to laugh or cry. This old man came through!