This is an overstatement. For most VCs, if failure rates within your portfolio exceed 50%, it gets hard to generate top quartile returns (unless you stumble on the rare unicorn). A more typical distribution for an early stage institutional investor (ie not a seed fund but a fund that leads investments, sits on boards, etc) is 40% of the fund failing. 25% producing >3x return (ideally with at least one or two >10x). and 35% sitting in middle.