This from AMD Forum Moderator concerning Wattman in Laptops:
ray_m Feb 15, 2018 11:07 AM (in response to deksman2)
Due to thermal issues, most laptops are not designed to support overclocking. Enabling Wattman on a laptop would enable BOTH under and overclocking, so it's disabled.
In case you don't understand THAT statement, Ray_m is saying since Wattman CAN be USED for OVERCLOCKING/UNDERCLOCKING even though you want to UNDERCLOCK it is DISABLED in Laptops. Overclocking and Underclocking involves changing CPU voltages.