is it just me, or after they changed the layout, 90% of the users left for reddit, so it would make much more sense if the speed boost would've been 1000%?
At that point they didn't have any users worth keeping anyway. The community had degraded to the point of irrelevance a year or two before the redesign. If anything the shift to reddit just harmed reddit.
Happily, subreddits help alleviate this 'content inflation'.
They aren't talking about latency, they're talking about how quickly stories reach the front page and how long they stay there.