Focusing on changes "under the hood" instead of flashy new user-visible features was the entire point of that release, it's not a myth at all.
Yes.
> it's not a myth at all.
The myth is that no flashy new user-visible features meant that Snow Leopard was a "stable" release. It wasn't a stable release, any more so than any other major new OS version. Snow Leopard became stable over time, after many minor bug fix releases.
Note the specific words I was replying to: "macOS really needs another Snow Leopard “no new features” release."
macOS doesn't need any new major OS updates. Snow Leopard didn't help. Mac OS X 10.6.0 was in fact much buggier than Mac OS X 10.5.8 preceding it. What macOS needs is a long series of minor bug fix releases.
This is crucial: as soon as you acknowledge that 10.6.0 was much buggier than 10.5.8, the whole idea that "we need another Snow Leopard" goes out the window.