I guess you could say that's true. They're much hardier than your average tropical fish
Ich usually comes from stress, such as too much temperature fluctuation, bettas are usually pretty resistant and tolerant of fluctuation, mine are anyway
A couple of mine had ick. BettaMax did not help. Methyblue did not help. QuICK Cure seemed like a miracle drug compared to the others. Ick was gone in under a week.