Sometimes problems that cause disconnections don’t happen on the player’s end (client) or on Blizzard’s end (server) but rather somewhere in the middle. Server restarts or maintenance also don’t tend to cause disconnection problems like this, so it’s unlikely that the restart or maintenance itself caused the disconnections to start for you.
It may not be something you nor Blizzard can solve directly, and instead it may be something that needs to be solved by one of the internet service providers that is carrying the connection between your modem and the Blizzard servers. Utilizing a different connection (such as a mobile data tether or a VPN) can be a good way to test and confirm if the problem doesn’t occur when re-routing the connection through a different provider. The WinMTR results shows instability in the connection before even reaching the Blizzard network, so this is why it was pointed out and suggested as being an ISP or internet backbone issue.
Lastly I would also like to mention that MVPs like Nicole and WyomingMyst are simply other players like yourself (not Blizzard employees). They’re simply trying to help shed light on possible causes and help explain / troubleshoot based on the technical knowledge that they have.