While I believe the golfer is on the right path because the hips are crucial in providing power in the golf swing, I have to wonder about a couple of things about the poster's process.
First, I think it's very smart and very crucial for a golfer to have some sort of serious stretching program. Flexibility is paramount to quality golf, longevity and health. So even if you have quality flexibility, a golfer should continue to stretch so they can stay healthy and prolong their longevity.
The first thing I question is the golfer's stretching program. Are they just stretching their hips or their entire body? This is important because the body sort of works like a chain and if a golfer just stretches one area of the body and neglects the rest, they'll likely never see the area that they stretched get that noticeable improvement of flexibility. Furthermore, you need to do the stretching program correct. It's not to say that the technique of the actual stretch is incorrect, but it is vital to breathe correctly when you stretch. Incorrect breathing means that you're not stretching the muscle all that much and you're likely to be very sore the next day.
I always suggest Roger Fredericks' stretching program at http://www.fredericksgolf.com/. It's a bit pricey, but it has three programs for the novice, intermediate and advanced stretching levels and gives you tests to help the golfer determine where they need to be. In fact, I often will do advanced stretching exercises for my upper body (where I am very flexible) and use novice stretching exercises for my hamstrings and calfs (where I am very stiff). Yoga is a good place to go to as well and does provide you with an on-site instructor to make sure you're doing the stretches correctly. However, yoga can get a bit expensive and beginners shouldn't try it at home so they will have to go somewhere to learn how to practice yoga properly.
The other question I have is what his swing looks like that made him work on hip flexibility. I'm assuming his hips are square at impact instead of looking like this:
I would highly suggest looking at the feet. Someday I'll come up with a YouTube video on it, but the golfer needs to keep the weight between the balls of his feet and the heel. If it gets on the toes, it becomes much, much harder to pivot the hips.
What I'm working on to get the weight off of my toes and to feel like the arches of my feet are 'suction cups to the ground' (credit: Shawn Clement) is to do the following.
- Stand perfectly upright
- Bend the knees to take your stance
- Raise the Toes up off the ground so you start to feel the pressure get towards the balls of your feet
- 'Suck' the butt backwards until the weight gets more towards the heels and is evenly distributed in the arches of your feet
If done correctly I should be able to draw a straight line from the back of the tush and it should be slightly *behind* the heels. Looking a bit like this:
This illustration has the golfer bent over a little more so the tush is behind the heels pretty noticeably. Ben Hogan was more upright so his tush was only slightly behind his heels.
As Homer Kelley stated in 'The Golfing Machine', there's only 3 absolute imperatives to the golf swing. So obviously there's many different ways to address the ball and having the weight on the arches instead of having it on your toes was not one of the 3 absolute imperatives. In fact, Laura Davies played for years with BOTH heels up off the ground at impact.
However, if you're struggling with your pivot and don't like your hip rotation at impact, check out where your weight is...particularly at address and you may find that you're more flexible than you think.