Well, everything on the web MUST be true.... I am kidding, but that State Farm commercial is pretty funny..bon jour.
You need to do some of your own research on golfers that keep the right knee truly flexed. I know of only a few pros who do it even remotely close to what the pros tell you to do. Keegan Bradley, KJ Choi, and KJ is really borderline, and maybe Carl Petterson, again borderline. All are very upright swingers of the golf club. All re-route the club to flatten it. Keegan has a great flattening move and I would venture to say it is probably un-repeatable for most of us mortals. Most people from such a upright swing plane are going to slice. That being said even Keegan loses a little flex.
What you need to think about is what is going to make you the best golfer. What will help you hit it far and straight. If almost all the pros straighten to increase their hip turns don't you think it might be a good idea? A pro might tell you something that is his feel, but that is not what may be happening.