All guessing I suppose.
Where's Martin with his answer that we may ... or may not ... believe.
I know Crosman re the Prems used to have Dies that they would run for a while just for Prems. After a certain number of pellets they would 'retire' that Die to be used for Accupells etc. It was also suggested that the lower grade ( non Prem ) pellets may have been from a mixture of Dies.
Daystate had Crosman make them the Daystate Li pellets that were basically Prems made on the same machines. Allegedly Daystate had their own Die.
Is it possible that Air Arms say to JSB ... We want pellets made with our labels on ... but we want first run of certain Dies. So after so many pellets then JSB use those same Dies for Exacts.
Or ... if there is a testing procedure re accuracy then AA say that they only want their pellets made on Dies that score highly in the accuracy testing.