Well you could do that too but you'd lose permissions between the two (NTFS supports POSIX permissions but Linux doesn't and vice versa with Windows permissions).
The blog post is really about making any Linux mountable FS available to the Windows side of WSL2 without NT needing to support it. E.g. it doesn't matter if the drive is NTFS or Ext4 or BobYourUncleFS as long as the Linux kernel can mount the FS you can mount it in WSL2 and access it from Windows without NT needing to support the OS. It also already works in reverse, volumes mounted in Windows (including NTFS) can also be shared with WSL2.
It's really just their integrated-into-the-OS version of VM guest filesystem sharing.