Google's Pixel phones never had the fastest chipset and that was by choice. The original phones used a Snapdragon 821 down-clocked to 820 speeds. The Pixel 2 and 3 also used underclocked chipsets, Snapdragon 835 and 845, respectively. The Pixel 4 was the first model to run its chipset at stock speeds. There's mounting evidence that the upcoming Pixel 5 won't even bother with an 800-series chip and use the Snapdragon 765 instead. To be clear, it could be any of the 765, 765G and 768G since they are all just different bins of what is essentially the same hardware (differing mainly in the CPU...
Source: https://www.gsmarena.com/the_pixel_5_may_have_to_settle_for_a_snapdragon_765_new_evidence_suggests-news-43309.php