The greys are a death sentence for the most part relating to the companies stock. Trading is very difficult on the greys as there are no market makers and no bid/ask. All trades are between shareholders.
Stock PPS on greys is significantly less, liquidity is far less, companies can't readily sell shares to generate capital, .... that is a small set of the issues...
This is grave but no longer a death sentence. And the SEC can thank itself for that.
I don't think that's clear yet. It depends to some extent on what the SEC does next. If they get some civil suits up and running in the next few months, that will serve as an additional warning.
From their point of view, they've let people know they need to be very careful about penny pot stocks. They've made it clear that there will be more suspensions. So people are playing at their own risk.
My guess would be that from early this year they've been looking at the MJ stocks one by one. And if they find something wrong, they suspend.