if you take a piece of gear and take a stack of say 50 standard empyral stamina infusers and use them until the piece doesn't let you anymore then try to use the higher tierd versions like advanced or ancient it won't let you when it should as they are higher tierd infusers.
Its the same thing with ability mod infusers. Its annoying to say the least, im not using standart infusers since i will get lower results on gear using em.