That depends. In this case, where the Lenovo drivers are clearly outdated and kinda broken, definitely they're the bottleneck for at least some games. That much they've shown, by installing newer drivers and showing a massive performance upgrade.

Although I'd caveat that by saying that their flashier results with big updates across OSs and driver variants are running at outright unplayable settings. They are benchmarking on settings resulting on framerates in the teens. When they say they saw 12% performance increases on the newer drivers they mean going from 14 to 16 fps in some cases.

Benchmarking properly is hard, I guess is my point.