I used to have a Mobvoi Ticwatch E entry level smartwatch. It was connected to my Samsung Note 8, which was in turn connected to my work Exchange Server.
When I put a Calendar Entry into Outlook on any of my work computers, with useful information in the Notes section of the Entry, it synced perfectly to the phone and I could read the Notes as well as the date and time etc of the Entry. From the phone, the Calendar Entry synced perfectly with the Mobvoi and I could see all of the same details, including the Notes, on the watch.
I then purchased a Galaxy Watch as an upgrade to the Mobvoi and, while most of the Calenday Entry syncs perfectly to the Watch, the Notes don't show up. This is an issue as that was one of the most useful features of having a smartwatch.
However, if I create the Calendar Entry on the phone itself or through a Google Calendar, the Notes sync perfectly to the Watch.
It appears that for some reason, the Watch isn't reading the Notes when they originate from Microsoft Exchange.
In case it made a difference, I've recently upgraded to a Galaxy S10+. Unfortunately, the issue is still there.