If you look further down on that thread you’ll see the following though:
Jan says compatible add-ons should be reinstalled and even back then I identified this behavior as a potential bug.
At a high level, the marketplace add-on jar files definitely do need to be removed during an upgrade same as official add-on jar files. However, if the versioning of the add-on’s marketplace title indicates it’s still compatible the add-on jar should be redownloaded and installed.
The bug I’m seeing is that the JSONDB files that is supposed to list all the marketplace add-ons that are/should be installed gets emptied out somehow so after clearing the cache it doesn’t see any marketplace add-ons to reinstall.