No Brave doesn't do that, its default behavior doesnt use crypto, its optional behavior theoretically lets you earn bat but not by processing cycles

Brave has its Basic Attention Token that they give users in exchange for sending notifications with ads in them. They literally pay users for their attention. Doesn't consume any CPU.

I think all advertising is inherently bad but this is the least bad form of advertising I've ever seen. Not only are users compensated, they can actually turn off the ads in the settings and simply use the browser normally, and it has a built-in adblocker even on mobile.