Again, you only have visibility to the POPs, so you're only seeing improvements on the path to the POP.
For example: there is no Google POP anywhere near its Oregon datacenter[1]. You literally can't just push your traffic to the Dalles and plug into the datacenter.
So, no matter where your customer is, you can only improve the traffic to the Seattle or the Bay Area POPs, where the traffic will move over to Google's private network.
Sorry, but I have to call BS on your claims...
Instead of routing to the nearest PoP, they route to the PoP that provides the lowest latency to their game server. I don't understand the confusion. They are simply measuring latency over a number of different routes and choosing the optimal one (for their use case).
Maybe you are assuming that there is no latency between the PoPs and the datacentres? I can assure you thats not the case.