No company can reliably test for edge cases - not Microsoft, Apple, Samsung, HP, etc. The resources that would be needed to a) identify every possible combination of usage and b) actually test said edge cases would be prohibitive for even Apple.
Good point. It's a question of degree. I'm claiming Apple is worse than what I expect, so it's definitely subjective.
Apple didn't bother testing what happens if you enter garbage input for the dns server (my computer crashed). They didn't expect anyone to do that; that makes sense. Is that an edge case that is justifiable to miss? There's no objective answer to that.
The real question is what happened with the update for @ldjpy. Also, there's another thread which I joined where someone raised the issue of strange SSD disconnect/reconnect since the update (and ethernet issues). I saw the SSD disconnect happen yesterday.
https://forums.macrumors.com/threads/did-the-latest-rapid-security-update-break-stuff.2388533/
It might be one of those edge cases since I have 3 SSD drives connected. Is so, then it's a judgement call again whether it's acceptable to not test thoroughly for multiple attached drives.