If you are doing so with the intent of supporting FF11.

Crysta is not a FF11 currency, it's a FF14 currency. If you bulk buy Crysta you are supporting ff14 because it is assigned to that games payment system, the only time Crysta is supporting ff11 is when you spend it on ff11 on that month.

I used to make this mistake and I won't be doing it in future, just a headsup to anyone unaware.

FF11 still belongs to ff14 operations so you're still supporting ff14 indirectly, but to a far lesser extent than just buying out a ton of crysta and letting it sit there in the ff14 account system.