I remember some discussing Nip05 itself isn't that useful to really verify if the user is real. For instance I think nostr:npub1sg6plzptd64u62a878hep2kev88swjh3tw00gjsfl8f237lmu63q0uf63m did remove his because of this. 
To check if is Saylor's real npub we should check if he posted his Npub on X and see if it corresponds