Did you miss where I listed the giant's hp? And I'm well aware that few people back then used average hit points the way they do now. From what I recall of modules at the time (at least from Dungeon mag), you were as likely to find a hill giant with 60 hp as it was to find one with 20.
Also, unless you have that super-high Strength, most powerful magical weapon, were at least 7th level, and access to a book that, IIRC, was often considered to be a bit OP at the time, you're not doing anywhere near the amount of damage I mentioned.
So sure, you could bring down an ogre or even a giant in one round... but I doubt that was the norm.