I heard on the news here in Texas that reporters indicated it takes a few days to switch, so while Griddy sent the email, their customers were not able to really act on the advice amidst the crisis.

That said, I think it was bad advice from Griddy for a second reason.

I think they should have told their customers to just go to their house fuse box and shut off their power to avoid the inevitable huge bill.

I'm not sure why others haven't mentioned this but the customers did ultimately have that recourse. This is the unfortunate but logical thing to do when your 6c/kWh bill grows to $9/kWh. And at least you can intermittently turn it back on when needed to heat your house for a short bit, etc which is still better than being totally out for 3 days as many people here were.