It really comes down to whether we trust Apple to do the work; auditors can be found that will certify anything you need even if not at the fraud levels of Arthur Anderson.
And this kind of thing can be hard to independently verify.
Given Apple’s track record I suspect they actually do care about this internally and spend the effort to make sure it is “real”.
I don't expect absolute perfection from Apple but I think they are putting in good faith effort towards these improvements and are just proud of their accomplishments.
If it was strictly a feel-good PR effort then that would have the complete opposite effect if their environmental claims were found to be fabricated, and it would just take one whistleblower anywhere in their own staff, their auditing teams, or anywhere in their global supply chain to bring down that whole facade.
And this kind of thing can be hard to independently verify.
Given Apple’s track record I suspect they actually do care about this internally and spend the effort to make sure it is “real”.