Australian pull ups are a great exercise but frankly it seems rather inefficient (time-wise) to simply add 1 rep per week when you’re already doing 20+ reps per set. Now if you’re only doing like 10 or so and adding a rep per week that would be more reasonable. Frankly, once you get to the 20+ rep range you’re fine with Aussies. I would suggest focusing your strength training on pull ups or chin ups and use Aussies for volume. They’re still a great exercise and totally worth doing for the benefits they provide to the rotator cuffs, but you will see much greater strength gains if you utilize regular pull ups for your strength training. The whole point is it should be hard, ideally 12 or fewer per set should be challenging. 20+ is endurance territory.