High odds usually have lower probability of happening. I don't think value bet gives you any edge or advantage over bookmakers because the likeliness of such games playing is low. I don't like betting in the lower leagues because the rate of manipulations and match fixing might also be high. Even in these low leagues, it is not certain that you will win when you find value bets.
They consider it as an edge because bookie sometimes refer only to the majority pick for the odds placement while in reality the match is the opposite just because the underdog has influence.
Value bets is not easy to spot if you don’t have deeper knowledge on sports betting.
Btw choosing value bets on most of your bets will make your account restricted as some casino specifically mention it as unfair.