I decided to research this subject because I like to be informed when I speak. The GAAP method allows the accountant to make a determination on depreciation that is informed by past experience, industry norms, and manufacturers claims among other things. The biggest thing is that such a determination must be reasonable and documented. So the accounting records should include reasoning for the depreciation schedule changing.
Considering all these companies hire third party accountants to come up with these schedules and there’s a consensus move between all of them, cooking the books as an explanation seems extremely unlikely.