As a quick follow-up, this appears to be an issue of very longstanding. There has been an issue open for NVDA (which describes exactly the same issue that's reported here, and actually includes a note that it happens under JAWS, too), that was opened all the way back in 2012.
This has been haunting screen readers through multiple Outlook versions going as far back as Outlook 2007.
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.
~ H.L. Mencken, AKA The Sage of Baltimore