What are you talking about? You haven't played it have you..
A packet of data moves at the same speed, regardless of the data contained within it.
Nearly every ISP has direct-peering links with Google, they don't transit some general internet server, it goes from your house, to your ISP direct link to a google server which is likely within a 1ms or less latency from the Stadia edge data center.
I play stadia regularly, with 4k HDR, with 2 of my kids also on 4k HDR, and 99% of the time, you can't tell that you're not playing on a local machine at all. We have Fios Gigabit internet, and we can pull 3 streams from stadia at 4k resolution and we only actually hit about 35Mbps of traffic, with a latency less than 15ms.