It's simple enough, really. People that talk about how things "used to be" often slip into a behavior of remembering things inaccurately, such as by remembering a 1e rule that was changed for 2e, or remembering an optional rule or house-rule as being the default rule in the book.
So when someone says they are talking about 2e, but brings up dying at -10 hit points rather than 0, which happened in the conversation before your post which I quoted, I like to cover the bases and inject into the conversation whatever is needed so that everyone can see what the default rules were in each of those very similar but yet shockingly different editions.
It's important to remember that how many games you experienced that went with the optional rule, rather than the default, doesn't actually change which was the default and which was the optional rule.
But yes, many groups that played 2e completely ignored or severely altered quite a lot of the rules (character death, spell memorization time, and class/level limits being the most common things to be changed). Interestingly, the things I've most seen complained about regarding 2e are actually a product of those rule changes, and have conversations about them which boil down to basically:
Gamer A: "2nd edition is way unbalanced because of X."
Gamer B: "...but the rule for X was actually Y, which provides at least some kind of balance even though not the best (a product of a better way of balancing things simply having not yet come along)."
Gamer A: "Y is stupid, no one ever actually used it."