Optimizing for benchmarks only gets you so far, and often a change that benchmarks well can actually hurt performance in the real world, so telemetry is vitally

Optimizing for benchmarks only gets you so far, and often a change that benchmarks well can actually hurt performance in the real world, so telemetry is vitally important for judging real-world performance. Since Google is pretty comfortable with adding telemetry, they have excellent data and deep insights into the performance (and hardware compatibility, and network reliability, etc.) problems that occur in the real world, and can design Chrome to meet those needs. Mozilla is unwilling to telemetrize All The Things, but in order to stay competitive they need to understand the problem-space at least as well as their competition, and so you see them tying themselves in knots trying to walk the line between privacy and useful telemetry.