The security setting is bypassable by the user. It’s just not a “hit enter to install a virus” popup, but the “disable secure boot” toggle in the UEFI firmware settings.
As anyone working in customer support will be able to tell you, if you give people a warning message they can bypass by hitting a button, they’ll smash their face into their keyboard until the unexpected message goes away and blame you for not telling them what they were doing.
The only exception are those weird machines that were built specifically to only run Windows. They’re not compliant with the secure boot standard. Don’t buy those if you don’t want to run Windows, because they’re designed not to. Or hack them, I guess, but that’s a lot of work.