LOL ... it's almost like the whole battle about sedevacantism.
Just as with the pope, there's a difference between deposing him and declaring him deposed (by divine law), so too here there could be a blur between dispensing and declaring dispensed (by divine law). Unfortunately, the way he worded it made it sound like he had jurisdiction over the entire United States.
Yes, an individual's confessor might advise someone that they are dispensed (if you are ill, you don't have to meet the obligation). Traditionally, only either a bishop or an actual canonical pastor could actually dispense someone, "I dispense everyone in this parish of the fast on a day in Lent that's the anniversary of the founding of our parish."
When saying that he's dispensing the ill and the elderly, well, no such dispensation is in fact needed, since the ill and the elderly (who are at risk from this thing) are excused by Divine Law and common sense. So the only thing he could mean is that he's declaring them to be dispensed ... but I think he's confusing himself here. SSPX has always played fast and loose with Canon Law, acting and pretending as if they had ordinary jurisdiction when in fact they don't.