To my knowledge, 1.0 was built when Cata was current, and the rebuild was completed while MOP was current. This documentary by NoClip has MOP imagery while talking about 'we needed to look at what the other games in the MMO space were doing, instead of thinking we knew best' so maybe that's Mandela effect'd me into my line of thinking. Google says 1.0 was shutdown on November 11, 2012, and that MOP released in Sept of the same year. So in order to use Cata (and only Cata) for their 'homework', they'd have to have been doing said research while still updating 1.0 with the earlier patch content, ie, back when they were thinking they could still maybe salvage 1.0

Also we have to remember, that nobody on the class design team actually mains a healer. Whether Priest was OP in MOP is neither here nor there, because they may well have played it 'wrong' and thought that's how Priest works. They may have seen a HPal in a dungeon run doing FOL spam and thought 'ah yes, peak healer gameplay'. They might have never tried Fistweaving in their homework phase, instead opting to just play Mistweaver at range (aka, incorrectly), if at all.

As an aside, I didn't know Chakra was a thing in Cata, the MOP version where it's like a Warrior's Def/Battle/Zerk stances made sense to me as 'ah this is why they added Cleric Stance', but the Cata version I'm reading about looks dangerously close to what I'd want to do with SGE (albeit, the effects lasting 4 GCDs, not 30 whole seconds jesus that's a long lockout)