Firstly, as Euler will probably come along and say later, GMA is basically a separate subject from Specialist.
... I would dispute this, but legit one hour ago on the train I said to myself, "I better come back later to let the this student know that GMA=/=specialist". #becomingpredictable #almostasbadaspiandphysics
But yeah - methods of proof aren't important to the specialist, new or old. I wouldn't stress - feel free to learn it for funsies if you want (inductive proofs are pretty cool, my favourite is the classic "add all the numbers from 1 to 100" one from Gauss), but if you're just going to learn it because "urghhhh, marks, study score, urghhhh" don't stress.
(Also, confirming Ned Nerb. Study design starts for years 12s in 2016 for maths, probs because not much has changed in them)