After the initial infection EBV lies dormant in reservoirs but can spring forth with a heavily weakened immune system. When it's dormant you won't test positive for the virus itself. The testing in longhaulers shows it's been reactivated.

That longhaulers shows up so prevalently in patients with mild Covid argues against EBV reactivation simply because of an initially weakened immune system. It seems Covid even in mild cases that have resolved can lower the immune system over time allowing EBV reactivation.

EBV reactivation could account for symptoms in some longhaulers patients. Patterson's monocyte encapsulated particles could also. But neither seems to be the underlying cause of longhaulers.