Its not hard coded to a specific level, its ratio based on your server/cluster population. Its not always the best thing to freeze, a lot of times people think freezing is the best, and everyone goes "Baaaaa" and freezes, ending up with an insanely competitive lower tier sage which is dominated by a few wolves also freezing and feasting on all the sheep.

Adjust your level accordingly based on your power and server./cluster whale level density. Sometimes its easier to farm at the top tier sage, sometimes its easier in the middle. It really depends on your individual position vs the power players in your server.