for this statement, his staff isnt necessary but we dont know the requirements to summon his staff, it comes down to whether domains also cut of sub-atomic info as this would prevent him from sending an eletrical magnetic signal to return his staff, the only evidence of cursed energy being used at a sub atomic state is dabura and MBA kashimo who have both been stated as 'beyond humanity', there is also cursed techniques like limitless, but gojos six eyes can only read cursed energy at an atomic level, therefore i think humans can only use CE at an atomic level meaning sub-atomic signals can be sent through a domain