The advantage is that you can do the CNAME swap atomically in the Cloudflare interface, instead of deleting a CNAME record and adding a new A record, which would lead to a few seconds when your DNS is entirely removed. Those few seconds may not sound like a lot, but they could be cached by Cloudflare or other external DNS resolvers, trigger "clean-up" functions within Cloudflare to remove resources associated with those domains, etc.

In our case, we have substantial logic running on the edge in Cloudflare Workers, as well as lots of other Cloudflare configuration options, and I don't even want to know what it could potentially do to our zone to remove the root DNS record that everything's tied to.