There are always active investors who could take advantage of this valuation mismatch and bet for/against specific companies that they think are undervalued/ove

There are always active investors who could take advantage of this valuation mismatch and bet for/against specific companies that they think are undervalued/overvalued and make money. Eventually this valuation mismatch would show up in their P/L statement and balance sheet. Passive investing freeloads on active investors - in a sense. That's all it is and I for one think it's great.