Well, I’ve gone to LSJ. The definitions I find there are:
ὑπερφρονέω
- Group I
- to be over-proud, have high thoughts (Aeschylus)
- to be proud in or of something (Herodotus)
- overlook, look down upon, despise (Aeschylus)
- (passive) to be despised (Thucydides)
- think slightly of (Eurypides)
- Group II
- surpass in knowledge (Aeschines); excel in wisdom (Hippocrates)
ὑπερήφανος
- overweening, arrogant (Hesiod)
- bear oneself proudly; living sumptuously, prodigally or insolently, brutally
- magnificent, splendid (Plato)
- sublime (Damascius)
As you can see, hyperphroneō “above-think” can mean both “be more knowledgeable than” or “think that you’re above”; but from those definitions, that seems to have been about generic pride, rather than overestimating one’s abilities.