The only thing there is, could be that some find it looks cool to stand narrow in "Greg" style - but you can do that anyways, especially if straps are wider it is easier
I find it hard to believe that Greg (and other followers) ride like this becouse it looks cool. It has more to do with having both foot near the center, so less movement and more flow in changing feet, that happens a lot in this type of riding. And becouse the wider stance is not needed since not pushing the foil to its limit and going long distances in the same direction. And it does not look any cooler btw. Only if we compare it to a race poo stance, than it does.
Just my toughts.
I also don't think its about style, but more about ability.
I mean the more you refine your sense of balance the more you can allow your self to "stand up" since room for error is a lot less. (center of gravity etc.)
This of course has its limits especially regarding the speed, so instead of going fast you go slow and change directions fast and this eventually can turn into dancing like moves with the foil and this is where the style comes from...IMO.
A couple more session and the transfer is complete. Wider stance is good for me. The longer story is this. Initially I set my straps up based on where the front foot went strapless, then spaced the back out accordingly. This ment I had good pitch control over the nose of the board but had heavy rear foot pressure. So I moved the foil forward to give me more even foot pressure. I hated the front foot further back compared to the foil. It ment too much stomping on the nose at high speed. I then moved the front strap forward back to a similar position relative to the foil. The result is I still have good pitch control over the nose and more even weight on the feet and far less rear leg burn.
I can also ride strapless small stance in between the straps.