We can be positive the entire motivation of Chrome is user behavior surveillance. There's not a nano-chance in all the multiverses that Chrome model is doing anything privately. They've gone to extraordinary length to accomplish this. It's not for free.
What did we expect when they dropped "don't be evil" from their company values?
But yes, there is a 100% chance that logs will get sent back to Google too.
Ooh, this is interesting. There's nothing stopping them from sending jobs down to local machines. That's some 3 billion nodes. We went through this with coin mining and spam botting.
Nothing stopping it except your ire if it's discovered.