How is this “Make ahead”? This recipe is listed as “Make Ahead”. But, I don’t see any comments or instructions on how to do so.

I can speak from experience and analogy about these tags at the top of recipes. They are added to member-recipes by site staff without consulting the author.
(Don't know whether they get agreement to tags on recipes by staff.)
In the the case of recipes I've posted, they are neither the most appropriate nor the most accurate.
So, in the case of the "make ahead" tag on the polenta recipe here, I would take it with a grain of salt.