Durability also requires the file system implementation and the disk to do the right thing on fsync, which, if I recall past discussions correctly, isn’t a given.
An application that really wants confidence in a write—to the extent that the underlying device and drivers allow—should use O_DIRECT. Or maybe there is a modern equivalent with io-uring. But that is not easy engineering :)
What OP is referring to is that some drives ignore that signal for performance reasons and there’s nothing SW can do to solve that part.
io_uring in no way changes the rules here.
But I'm not sure I'd necessarily think of O_DIRECT as a way of improving "confidence in a write". It's a way to get a specific behavior.