That may not sound like a great study, but I tend to agree with it. I found when doing martial arts that stretching up for a long time (static stretching) made me go kind of wobbly, and I noticed a similar effect with the golf swing.
The most effective program I found involved warming up by duplicating the actions of my coming activity, gradually increasing the speed and range of motion - dynamic stretching. Too much static stretching always seemed to interfere with my athletic action, and it was better to train for flexibility itself at a separate time.
When I first became certified to teach in a gym (around twenty years ago) we were required to teach subjects to stretch at the beginning of a workout. Personally, I found this to lead to the shi**iest workouts, with low weights, poor control, and few gains. It appears to be now accepted that stretching slows down the muscle for a time; perhaps 30 minutes, maybe up to an hour depending on how hard the subject stretches.
I have suspicions about stretching, and wonder how many golfers have 'lost their swing' through too much static stretching. If I had a well grooved, high performance golf swing, I would look to keep it in that groove. That is not to say I am against stretching completely, just saying it has a place, and more research is needed on the subject.