Not all charges can be PoT'd, though. In general you still have to pay the entire statement balance each billing cycle (it's a good habit to have when using credit cards anyway).
To add to this as well, this can be disabled, but it's on by default for new applicants. They can put a limit on the charge cards as well, so it can be almost an ambiguously limited credit card now. That said, I don't think being given a set limit is very common, or very impactful for the average person unless you're a large spender.
I have yet to see a charge on my Amex Platinum that wasn't eligible for pay over time. In practice, I would say it's not different from another credit card at this point.
I believe each transaction has to be over $100 and there's a total limit on the number of pay over time plans you can have active. But yes, other than the dollar amount, I've not seen anything not be eligible.
They changed this a few years ago with the "pay over time" feature on those cards.