Smooth posterize time?

Hello, I am looking for some help. Very often I keep noticing in adverts and some high tier animations the use of posturize time, like 12fps but it seems to be in combination with something else that it looks smooth, noticing it mostly on text.

As if it comes in at 12fps and quickly raises to 24 right before it's position. But when I experiment I can't get that crisp look.

Sorry I can't find any examples right now, Does anyone know what I am talking about?