It sounds true to me.  The only reason I don't earn exactly 4x what you earn is because we don't adjust our investments to be equal to each other after every roll.

I risk 1% and win, my investment grows more than yours, since you only risked 0.25% and won.  Our bankrolls were equal before the bet, but mine is now slightly bigger than yours.  (101 vs 100.25).  If we both immediately divested our profits, bring the rolls back to 100 each before the next bet, then I'd always win (or lose) 4x as much as you.