This is only partially true. By default, homebrew supports (or, in their terminology, taps into) two repositories, homebrew/core and homebrew/casks. Core only

This is only partially true. By default, homebrew supports (or, in their terminology, taps into) two repositories, homebrew/core and homebrew/casks. Core only takes free software, built by the Homebrew developers itself, installed in /opt/homebrew etc. Casks takes everything under the sun, including commercial software with no available source code. Such software is often downloaded straight from their developers and installed wherever it wishes to be installed, most often in /Applications.