But my guess is it varies by property. For example, in the post you mention it says that the GM of that particular property said that she wouldn't give out brekkie certs for legal holidays, which one could conclude is (in cova's example) Thanksgiving Day only. But others have mentioned getting brekkie certs. So seems to be up to the property.

I agree w/ the last line of VA1379's post - wishing for clarification from Marriott because it isn't clear on the website.

Cheers.