> Aside... one of the design decisions Microsoft took that absolutely blows my mind is using `\` for file hierarchies instead of `/`

That decision goes back to MS-DOS 2.11, circa 1983. (DOS 1.0 didn't have subdirectories.) The model for DOS directories came from UNIX, which at that time was the very aggressively defended intellectual property of AT&T. As Microsoft was an AT&T licensee -- for Xenix, their version of AT&T System 7 UNIX, which was Microsoft's vision of the future of operating systems when PCs became powerful enough: they licensed it in 1978 and resold it via OEMs -- I speculate that they were afraid that AT&T might sue them for patent or copyright violation relating to the filesystem design if they went with a forward slash.