I heard they drop on 6/7-Star raids.
This assumption is being overlooked. I don't... "think" any people playing these games are using wifi/online features. In the past, Nintendo used online to detect people playing hacked Switches and playing games that aren't released yet, and then subsequently bricked their system, so I'm sure many people playing the early release are offline.
If there are any features hidden in online gamemodes like high tier raids, we won't know about them until release.