Just my take: Bearing i mind that I don't have to produce written scores for what I do (music for my own sake), I find that the only way to get the exact performance I want (I use mostly CS2, CSS, and CSSS) is to move note start times by hand. I have become accustomed to this and prefer the workflow as I get precisely what I want.
My favorite aspect of the Cinematic libraries is the single instrument with keyswitched articulations(I hate having to part out lines for separate articulation patch/tracks). In the stuff I write I usually jump around articulations aggressively, so I can't get the response I need with an overall note onset "offset". That might make my legato sing at the right time but then my stacc/spicc/marc would sound early. So I have happily embraced the practice of grabbing chunks of notes and sliding them by eye (with snap off) as needed. (If one uses keyswitching one has to do this anyway to get the KS in front of the phrase that needs it.)
If I had to present a written score I might save a version of the piece for that purpose and go back and quantize to line things up for printing.
But this isn't limited to strings, as others have said. The same problem occurs where "feel" needs to be imparted, a simple example being "swing". There are also lots of cases where urgency is manifested by being ahead of the beat too. So for me it all comes down to hand-crafting for the polish needed for expression.