Wasn't a lot of Snow Leopard an exercise in removing old cruft from the PowerPC architecture, and the last release to support 32-bit Intel machines? From my perspective at the time, it was really meant to set up Mac for the next decade or so, which it did brilliantly.

That's not how I remember it. In fact, Snow Leopard was no less buggy than any other release, I'd say. As explained in the article, that mythology of a stable release was formed over time later on.

Mountain Lion dropped support for 32 bit kernel. I only know this because Apple didn’t provide a patch for first generation Mac Pro users, even though the CPUs were 64 bit and could run Mountain Lion just fine.