Another point is that when installing Snap packages from the command-line, the verification tick only appears after the install has finished, by which point it is already too late.
You can view package info prior to installing, but if we're talking about a typosquatting issue here, that doesn't really help.
I think the main mechanism of this is communication directly with developers on forum.snapcraft. In this case Mozilla with Canonical etc...
I didn't go through this process so I don't really know.
I think that is how it has worked so far for all of the 1st party snaps I have seen.
I read something the other day about needing to pay Canonical $15k/y for a branded Snap store, but I'm not sure if that was about private stores, this, or something else.