The stock plates do have some slop. What Danny is saying is that it's useless slop. You'd have to slot the strut tower to allow the stock plates to move where you'd need them. When you have the stockers jammed into the corner of their holes, that essentially makes them non-adjustable (in terms of allowing you to dial-out neg camber and get adjust meaningful caster).
It's kinda like my seat track - sure it's adjustable. But I have it jammed through the rear-most adjustment and my knees still hit the dash. Adjustable, but not functionally adjustable for me.