Well, I can't say for sure, I didn't play beta or the released game. But I do recall several "first impressions" articles complaining about lack of pause (I think RPS did one), I know they got to play it, though not what version, I assume it was true at one point. You'd think this would have been more heavily promoted as a "feature" since it was a major knock on the game early on (several of the threads here locally went on ad nauseum about it, no one playing beta saw this and thought to point it out?).
Still, sometimes the "whiners" are actually the people who prompt the fix. If they are lying about it and know better, sure it's FUD, but people bitching about it months ago, it being fixed, the fix not being general knowledge, and people still whining about it isn't really FUD, it's misinformation, sure, but the purveyors have intent to inform, they're simply misinformed themselves. And the original folks weren't spreading FUD, it was true when they said it (and true for the forseeable future, presumably).
So, you may have those original people to thank for your ability to pause, or not, Blizzard probably isn't willing to say.
Yea, I remember that people were saying that you cannot pause the game. You definitely cannot pause it if you're playing a public game (even if you're alone, maybe that is what they have been crying about?). The hotfixes say nothing about a related change.
... looking through the patch notes right now...
It is no longer possible to prevent character death in a single-player game by pausing the game in one game client and then logging into the same account from a different game client
The only thing related to pausing the game (I read through all patch notes, didn't just search for keywords, so that I wouldn't miss anything).
Maybe they implemented a silent / undocumented fix during the first few days, can't say, as I got the game a few days after its release (well, the Starter edition) thanks to a key from FraterPerdurabo (thank you!). As far as I can remember, the game was pausing back then (even though I tested it several days ago in various situations, never died, and enemies were always at the same spot after resuming).
EDIT: Solo-ed the Butcher. Didn't die a single time. Can freely solo Act 1 now (talking about Inferno), but going to stop for a week or two to focus properly on my undergraduate thesis.