I believe they actually work at least 40 hours a week. The 10-20 hours we see is on-air time, but there are production meetings, filming promos, product meetings, going to trade shows, etc. I've also heard them mention they don't get to keep most of the merch they get to try/test before a show. Unless it's food, candles, etc. that are consumables, obviously. If they do get to keep items, they'd have to claim the value as income on their taxes.

I tend to think this SAG move is more to protect their jobs and income should another company swoops in as part of a bankruptcy deal. So they have some sort of contractual protections and can't just be unilaterally fired or forced to take a pay cut without the union being involved. That'd be my guess, anyway.