This is a blatant lie. Google will share this data with law enforcement, also on request by evil and/or totalitarian regimes.
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And even for use within a Google:
It is as believable as FB promising to not use 2FA for other purposes.
And malicious tracking of users who explicitly demanded to stop doing this is just another proof that noone should trust it.
It is likely that Google sooner or later WILL use search history for own purposes.
I am not even really trusting that Google is not saving my location in real-time despite that I switched this off.