"If a publisher has not verified ownership, then a user’s contributions will be held in reserve inside the browser for 90 days. [...] At the end of the 90 day period, any contributions marked for unverified publishers will be released back to the wallet. No funds leave the browser except to go to verified creators."

https://brave.com/faq-rewards/#unclaimed-funds

[This post describes the behavior of Brave Payments in last 2018. It is not an accurate description for how the system works today, in 2021].

No, creators did not have to be savvy enough to make their own ERC-20 wallet. We worked with Uphold at the time. Creators could verify with Uphold (a wallet would be created for them), and we would then send Brave's BAT (earmarked for the creator by Brave users) from our own settlement wallet over to the creator.