Afaik, this is the policy since day one.
It was aimed to be a FAQ site -- not just a question-answer site.. That's why it have community answer, allow the same poster answering his own question, encourage duping, allow other people to update/correct an existing answer,etc.
Back in those days:
1) Moderator knew the subject.
2) Most questions are "frequent" enough to qualify as FAQ.
3) When duped, the old answer is less likely to be outdated (because the site was new)
That doesn't really show that it was a common complaint given it accrued zero Reddit agreement points.
The situation now is also much worse than it was, because answers could be two years out of date then and beyond a decade out of date now.
I quit when I realised I would be scrolling by walls of jQuery answers for the foreseeable future if I kept using the site, not worth the waste of my time.
In the old days, moderators were encouraged to update the old post. Many stopped to do that when people complain their post were edited by others, or the votes goes to wrong person because it was edited.
I even checked to make sure I wasn't misremembering things - here's someone complaining about the same thing in 2011: https://old.reddit.com/r/programming/comments/cm02a/you_cant...