Windows NT 3.5 (1994) would beg to differ with its support for IO completion ports (IOCP). I think io_uring is more general and more flexible for the sort of M:N scheduling systems now commonly used in programming languages, but IOCP predates io_uring by 25 years!
The rest of your comment sounds right to me, there are unanswered questions about how DirectStorage interacts with filesystem filter drivers.
io_uring does have a more ergonomic and POSIX API, but that's because it's on Linux! Fundamentally they're both completion port based replacements to polling for IO events and they're both capable of high throughput and horizontal scaling.
Essentially, it's about streaming game textures directly into the GPU memory.
The idea is that this is highly asynchronous and parallel from the perspective of the CPU, so trying to do this through the "main game loop" would be an absolute nightmare to code at the scale we're talking about here. Think 50K IOPS sustained at 8GB/s with pretty hard real time guarantees.
I haven't been able to find any real technical details about what DirectStorage really is, but my expectations are that it will consist of:
1. An asynchronous IO API allowing for low-overhead submission of IO requests from the application to the kernel, including batch submissions and reaping of completion events.
2. Some provision for transparent compression offload, either to the GPU or to a CPU-based fallback
3. Optional support for peer-to-peer DMA transfers of data from SSD to the GPU's VRAM
Linux is already the gold standard for (1) with the relatively recent io_uring API, and has support for (3) to some extent (P2P DMA has been a fairly obscure feature until recently).
There are still some pretty big unanswered questions about DirectStorage. How well will it reduce the IO overhead that currently allows antivirus and other programs to hook into the IO stack? Will it be compatible with non-Microsoft NVMe drivers, including Intel's RST drivers that are commonly used for their software RAID? Microsoft doesn't seem to want to make that kind of information public this year.