My understanding is that the current "Big Beautiful Bill" reverses this
Do not think that is correct. The original accelerated depreciation is simply not being renewed.
IANAL, but the language of the bill seems to suggest GP was indeed correct:
https://www.congress.gov/bill/118th-congress/house-bill/7024...
It seems they're going back to the system where one could choose to amortize those capital expenses, but not be required to.