I engaged with the folks pushing this feature internally when my own browser started enforcing omnidirectional login. One of my specific complaints was that it was an end-run around the user-provided sync passphrase, which nominally prevents Google from hoovering up my logged-out history. They didn't grok my privacy issue. Maybe they were deliberately misunderstanding me. Doesn't matter either way. Now I use Firefox.
This feature doesn’t enable sync. That’s something that members of the Chrome team have been patiently trying to explain to Matthew Green on Twitter for several days now. [0] https://twitter.com/__apf__/status/1043505744144826369?s=21
So in theory your data should remain local
That doesn't sound very reassuring to me. Especially long term.