Using older versions of Outlook for Mac for personal email and calendar
This is not a solution, but maybe it may help someone or progress the case in some way.
I have been "punting" while this debacle is supposedly in the process of being resolved.
That is, I have been searching in Finder to find certain emails as the need arises.
However, I noticed that, if I click on an email file in the Finder search results and Outlook opens the email, then Outlook will then be able to see & find that email in the Outlook search results. I then tried opening 64 emails all at once and that also worked in terms of adding more search results in Outlook.
Unfortunately, for some reason, these Outlook search results seemed to show up only while I had my search word typed in Outlook. After I deleted the search word, the results disappeared as expected, but would not reappear when the same search word was re-typed. Very strange.
I am not sure how this tidbit might be exploited as even a temporary work-around. Maybe it will help to find a certain email since the preview will at least be visible as long as the results are still showing.