If you have pens in the building, and staff need a pen, they will use the pen that is available, even if there’s a sign saying “not for purpose x”. If you want to stop that happening, you need to not have limited pens available to your staff at all.
Humans see a hammer and a nail and don't think about the rule saying "rubber tipped hammers only in this area, flammable vapour present".
It could also be as simple as "anything tainted by the Claude non-targeting-conditions can't be used in target selection, and we don't want to leak classified information about which components we use in target selection by requiring specific items to be developed without Claude, so we can't allow it anywhere".