To perform actions, a UDT agent needs knowledge about the world to the same extent as any other agent does. The distinction lies in when (or what for) this knowledge is needed: an updateful agent would use this knowledge early in its decision making process, while an updateless agent can be more naturally modeled as first deciding on a general strategy chosen once for all possible situations, and only then enacting the action prescribed by that strategy for the present circumstances. This last step benefits from having accurate knowledge about the world. (Of course, in practice this knowledge would be needed for efficient decision making from the start, updatelessness is a decision making algorithm design principle, not a decision making algorithm execution principle.)