I was under the impression that Firefox Focus blocked ads in some other apps as well but that doesn’t appear to be the case indeed, at least not in Chrome.
Firefox Focus ships with a content blocker extension, I think, so it can block ads in Safari and third-party apps using SFSafariViewController. Chrome uses a webview, so the content blocker won't work there.
Actually, they only work in the specific case of SFSafariViewController. This isn't available for any old webview to implement.