We've spent a lot of time identifying bottlenecks and fixing them, up and down the stack, with FUSE being just one of them, even the AWS SDK itself introduces its own set that we've addressed. cunoFS can also be used with FUSE, and we find that it is roughly half the speed of non-FUSE (but thanks to our other optimisations, this is still much faster than alternatives).
It's company trying to sell things to you, and it's a benchmark that just happens to show their product in good light. They have lots of reasons to spin things their way.