But one of those was a big compatibility breaking one that I hadn't done the prep for (because I'd missed the whole lead up for various reasons and was months late on the update anyway) and I still can't really explain the other.
Compared to Debian which I managed to break many times in the same time frame...
How did you exactly break Debian multiple times?
I've read about people doing crazy stuff, like replacing the default compiler entirely (rather than setting an alternative one) or forcing apt to install incompatible packages... and then complaining that the distribution is not stable.
Non-rolling distros are very very conservative with package upgrades, and they don't "just break", as little changes over a given version.
Alas, I can't remember exactly what happened but it was the late 1990s/early 2000s - no crazy stuff involved, just things getting confused / crashing whilst doing updates and leaving things half-arsed and broken.
I'm honestly not quite sure what you're talking about. I've been using Arch as my daily driver for maybe 5 or 6 years, and I don't recall ever having my installation messed up from an update. Arch is fair bit along the spectrum of being a "build your own system from the ground up" type of deal though (although not quite as far along as something like Gentoo), so I don't doubt your experience, given how much two Arch installations can differ.