Because some of the potency values shown in the tooltips are absolutely bonkers?
I do agree that assumption is a risky business at the moment though, go back to HW or even NIN beforehand and SE clearly demonstrated a habit of being over cautious with new jobs to seemingly try and avoid disrupting things so to speak. The 3.4 buffs to AST seemed to suggest a more Blizzard style approach to getting the job played aka 'buff it till it's OP'.