Normally I would disagree with you and say it's not feasible to really test on every video card, processor, Operating system combination. The problem with that defense however is that the stuttering seems to be present even for people with beast rigs.
Honestly I would love to hear what video card/processor this port was optimized for because it's not the ones listed on the system requirements.
Unless they tested it on like a 6,000$ rig with a beast vid card and processor I don't see how they could have NOT encountered the stuttering months ago.