It is interesting dono that for this talent you don't ascribe to the 'common sense' approach and feel that more clarification text needs adding, whilst for other rules queries you have said that added clarification text isn't needed as people should use 'common sense'.
I would say that if the rules are brief, then take them as they are and use common sense for the rest.
I think that's part of the problem in this instance, is that the rules are brief. Having done RPG design work both officially and unofficially, I've run headfist into the issue of too much brevity.
Could be that to me, Quick Strike equates to the d20 Sneak Attack feature, only instead of working against flat-footed/unaware targets like Sneak Attack does, the Quick Strike talent just means you got the drop on your target in some way. Also from a lot of time spent playing Star Wars minis, where similar abilities (bonus to hit and/or damage if target hasn't acted/been activated that round) existed, namely Advantageous Attack (bonus to damage) and Cunning Attack (bonus to hit and damage). Maybe part of why the official response was "per encounter" was a reaction to how easy it was in D&D (particularly 4e) for a character to get their Sneak Attack damage on a round-to-round basis.
That and one of the cases against Quick Strike being a "per round" was that it was deemed too powerful. And yet, for a paltry 350 credits, a character with a blaster carbine/rifle can enjoy a Boost Die to all their attacks no matter when they act in the round via the Forearm Grip with the Mod (Accurate +1) quality. The cheapest that Quick Strike can be obtained is at 10 XP and only under 3 specializations that are each under a different career.
Plus, for those specialications, it's pretty much a required talent if you want to advance further along the talent tree, and one thing I strongly dislike is a player feeling like they are being forced to spend valuable character resources on something they may only occassionally get to use.
As for "common sense," I'd be wary of using that as a blanket statement, given that a lot of folks' "common sense" told them that the successes leftover after the initial one to hit your target was accounted for (i.e. rolled 3 successes, damage bonus is +2 for those 2 successes above what you needed to hit) rather than what Jay clarified it to be.
By the same token, the "hasn't acted" could also be taken to mean that if the bad guys do something that triggers a combat encounter, even if it's not attacking, before initiative is rolled, then they've technically "acted" during the combat, and Quick Strike would be useless. Probably not the intent, but one of the players at my table posed this question (for what it's worth, he's a contract laywer by profession, so exact wording is a day-to-day aspect of what he does to provide for his family), and I doubt he'd be the only person to wonder something like that.
Maybe I am overthinking it, but after 20+ years in this hobby and exposure to a wide variety of RPG rules (some good, some not so good), I tend not to just accept rules at face value without thinking them over, if only to try and get a better grasp of what was intended rather than simply what was written.