At least one semiconductor company has an internal simulator that allows the user to specify looser tolerances on select subcircuits to help speed up the simulation. The idea is to allow reduced accuracy on purely-digital blocks, etc.
Is this possible with spectre?
This is a capability that is common in FastSPICE simulators (such as UltraSim) where golden accuracy is not so important compared with verifying functionality. It's not possible in Spectre.