Why does this matter? GPU performance has been good enough for 10 years. Any phone can play a high res video, what more does it need to do? For a new phone it's AI performance that matters and supposedly that's what the Tensor is optimized for. The traditional areas that have not been good enough are battery life so relative efficiency matters and how good are the radios.
Why is anyone still surprised by this? Tensor is basically the cousin of Exynos.
If Exynos is lagging behind, its inferior cousin will probably also lag behind.
People buy a Pixel phone because they are obsessed with the 'Google experience', benchmarks don't matter to their kind.