Balta is an odd example to use for your point as he is a literal Goliath. The bloke has a massive upper body.
Also, big arms aren't necessarily the be all and end all, but you do surely get the correlation between size and a players propensity in the gym and genetics, and therefore strength.
This is the elite level, they have programs designed for them and guys with greater size and mass have that because of these programs to improve performance.
Larger arms and upper body is just an easy way to visualise that to the naked eye. A players muscle development is usually in proportion, they're not sitting in the gym doing bicep curls and nothing else, if a player has big arms it's because his overall physique has been developed well for AFL.
That's not the case at the amateur level where you can just focus on making your arms big to look good without much else supporting it.
Not sure all players are in the same proportion, which seems to be what you are suggesting. I would wager there are major differences in the proportion of some player's upper leg muscles versus to their upper arm muscles compared to other players. I do accept though that players will have taylored programs designed to improve their functional strength across their whole bodies.
That aside, your post just about all makes sense except Balta isn't my example, he is the player nominated by the poster to whom I was responding:
I watched the Lions / Blues game last night.
Charlie Curnow's arms are bigger than our entire squad combined. That guy is a elite physical player. We have no one close to that level of fitness & thats what a power forward needs to look like. Balta is not close to that physicality at this point.
So you should be setting that guy straight not me.