They ask a bit of trust on that, but their FAQ also has an appeal to reason:
I have privacy concerns over linking my search queries with my credit card. Why should I trust you?
We do not log search queries. Queries you type are never associated with your account. The simple reason is we don’t have any reason to do so, as it would only be a liability for us. We are in the business of selling search results, not user data.
(For the record, I use Kagi)
I’d ask why they don’t make it optional (I’m not a Brave user) but it seems it was.
Given that, I’m inclined to agree with the decision to remove it. Pick your battles and live to fight another day.