This is interesting, I suppose AirArms either lied to you or something has changed in the meantime... I live in Czech Republic and I recently contacted JSB with the question if the pellets are really one and the same and if there are any different tools owned by Daystate/AirArms/Cometa etc... Today I received my answer... the conclusion is: whatever is the cheapest is the choice to buy. They are one and the same pellets made by one and the same tool(s)!
Here is part of the email (I will translate it for you below):
Diabolky prodávané níže uváděnými společnostmi jsou výrobou naší společnosti. Vyrábíme je na vlastních strojích. Distribuujeme do dalších zemí prostřednictvím obchodních partnerů, kteří mají na krabičkách vlastní samolepky. Jedná se však o totožné střelivo vyrobené naší společností. Veškeré diabolky, které uvádíte, můžete zakoupit v naší provozovně v Bohumíně-Skřečoni, ale pouze s naší samolepkou JSB.
TRANSLATION:
"Diabolos sold by the companies you mentioned are manufacted by our company. We make them on our own tools. We send them to other countries through business partners who have their own labels on the boxes but it is identical with ammunition which is made by our company. All the pellets you mentioned can by bought at our shop in Bohumín-Skřečoň but only with our JSB label".
FYI - the companies "I mentioned" were: Daystate, AirArms and Cometa as examples.