Well, it doesn't go into detail in the
Wiki, and your explanation of the issues with Ice beam offered a simple logic. Mind explaining?
As I understand it, Cartridges are condesnsed mana. To make the cartridges, you use your own mana, which would hold your affinity. Burn the cartridge, it releases the stored mana through your core in a burst, and you cast he spell without the needed windup. The problem with Ice beam is that it still suffers the conversaion issue same as normal. So the mana you're injecting still has to be converted, twice, before being used. But if you converted the mana before condensing it into the cartridge, then the conversion process could be bypassed under battlefield conditions.