I understand. Class-actions are meant to hurt the defendant financially and settle for large amounts and make them accountable for their actions, not to benefit the plaintiffs unfortunately.
This is not always the case. I owned a home in the '90's that was plumbed with polybutylene piping which turned out to be a disaster waiting to happen. As the result of a class action lawsuit I qualified to have all the polybutylene piping ripped out and re-plumb the entire house with copper piping as well as receiving full reimbursement for the repairs and damages from two previous leaks that I had. The total bill for the plumbing, restoration and damage reimbursement amounted to several thousand (1995) dollars and didn't cost me a penny.
Of course the scale of that kind of problem was orders of magnitude different than having a slight performance degradation from a worn battery in a phone. But I'll take the $25 anyway since I own an iPhone 6s Plus.