I've been playing tennis for a long time, and I've never heard of the steak knife grip. I'm not aware of any coaches that are teaching the "steak knife grip." Is the steak knife grip a continental? An eastern? Or somewhere in between?
If you want to learn the grip that most of the pros use, put your index knuckle on the top bevel. If you start with a continental grip and shift one bevel over you'll be in an eastern grip.
Let me reiterate what Cheetah and Borami have already said, most pros use an eastern grip. If you look at Wawrinka and Federer's topspin backhand grips, they're not extreme at all. Federer is closer to continental than some of his contemporaries.
If you're learning the one-handed backhand, using an extreme grip will not magically help you tap into the modern game and give you a Wawrinka-like backhand.
Henin probably uses a slightly more extreme grip because she is shorter, and probably grew up having to hit a lot of shoulder level balls. Everyone should use whatever grip is comfortable for them. Everybody's grip is slightly different.
If you were never taught the basics of a one-handed backhand, gravitating towards a more extreme grip is not a magical passport into the modern game. It would be a better use of your time learning the basic mechanics of the stroke.
The trend I've noticed is a lot of players of average size or bigger, are using smaller sized grips. I'm not sure if that's the ticket to the modern game, for someone who doesn't understand the basics of the backhand. But if you're looking for trends to follow in search of the modern game, that might be an actual one.
As far as the grips, most guys use eastern. Even look at the clay court guys. Some examples I can think of are Gaudio, Robredo, Almagro, Costa, and Corretja. All those five use the eastern backhand grip. If you're just learning the stroke, the eastern backhand grip is the most common in today's game, and it's a good place to start.
You can experiment and toy with your grip and find the exact position that works for you. It will vary based upon your height, playing style, and preference. Some people even shift their grip a little depending on the conditions.