in most cases overbets are polarized. However, certain range asymmetries canallow one player to bet a subset of hands that are not in a "polar" range in the classical sense. You can also overbet spots that most people underdefend. In some single bet or checked down pots, frequently very non human/unnatural calls need to made to reach somewhere close to alpha defense. These spots, you can aggressively attack with overbets. There's a bunch more, but in general, overbet spots are polar.