It's pretty easy for those to be race conditions, too. Plenty of one time crashes in a fleet of thousands of machines with ECC. ECC lets you know it's almost certainly not a memory issue.

10% more fps doesn't matter at 150 fps, but it's nice when your FPS is lower. 60 -> 66 might mean you don't dip below 60 as often. 55 -> 60.5 is pretty nice too. Maybe less of a deal if you've got VRR etc.

> you can't tell the difference with 150 FPS and 165 FPS

First byte latency makes cache misses significantly slower which in turn makes 99%ile latency (which is perceived as microstutter by humans) significantly higher even if it doesn't affect throughput (fps). This was well documented way back when the first DDR5 sticks came out and they performed like crap compared to overclocked B-Die DDR4.