Of course, but I’ve also seen scum “outed” as “fool” under the same reasoning.
And even if that never happened it would be besides the point, since the claim isn’t that fool is easy, but that fool makes the game worse.
The fact that a fool is even enabled to act 100% identically to a scum (again in ways that a scum trying to appear BD simply can’t) is a problem, even without the actual existence of a fool doing so.
Every single scum read could be a fool faking it, or just a fool playing pro-scum moves in order to make it genuine (which will be completely identical to a sellsword for the purposes of scumreading).