The swing is a dance/waltz.
The X step helps us flow through the dance allowing us to keep our weight in balance and check when done properly. As well, a proper x-step helps you load into the plant.
What most end up doing is seeing pro's make this Massive x-step and they mimic that and leave their toes so far out that they loose all the benefits from the balance and the drive from the rear leg into the plant.
You don't really need to "run up" to do this. If your x-step is solid, and your balance is good, you can drive from the rear leg into the plant generating more force. This is why I'm not very huge on running at your throw, you're taking it from a dance to a sprint. And when you run, you're essentially falling forward but continually catching yourself to propel yourself forward.
So, if you're starting from a run, you're already starting off balance as you've not learned that balance mechanic yet to keep your weight centered.
Then we look at pro's with this larger x-step, that comes from keeping their balance centered while moving at a faster rate to gain some power into the plant.
Standstills can generate a ton of power with proper mechanics, but I think they require more mechanics than using the x-step to generate that power. So for lower powered shots that require more finesse and accuracy, a standstill is far better practice than any run up or step style throw as we can set our base on the target line and do the motion.
But in turn, a standstill encourages more muscling in the throw. Learning to drive with the body on a standstill I think is a great thing. But it's harder to remember to drive with the body on a standstill vs using the x-step. As the dance encourages flow vs a mechanical style motion.
So the X-Step can be a bit of a challenge in a way, because if you're not balancing properly, and orienting your feet in a way to provide you power, you can slip into other bad posture/balance issues that will limit your power more than help your power.
And its very easy to get sloppy with your x-step as you go through the circle of practice.
Our bodies are lazy, and they will always try and take the lazy way out, and a power throw requires you to not be lazy. It needs the wind up and the flow, not the half motions that we tend to lazy our way into.
I struggle with shoulder turn and hip turn on this particular thing, as with back issues and such, I'll get lazy trying to protect my back, but in turn damage my shoulder as my body doesn't go through the full range of motions needed and I end up muscling the disc vs driving with my body.
As with a lot of things out there, it's important that we set things up for success. And part of that is to dance to our full potential on the swing. When you build something, the more time you spend setting up, the easier the job is.
So the more effort you put into your setup in the swing, such as the hip load, balance and back swing, the easier the swing will be as you're set for success, vs trying to rush through it.
This factors into putting as well.
5 footer or 50 footer.
Go through your routine, do all the motions for a putt regardless of the distance. Don't take the lazy way out, even though its a tap in.
As for pro's in their practice swings, I have no clue what they are doing half the time, cause I'm watching them do their practice stuff and routine and 90% of the things they are doing dont look like they are actually trying to set their brain/body up for the shot.
Holding the disc 3 feet higher and looking down it before throwing the shot, that stuff makes no sense to me. You're not telling your body what you want to do by holding the disc 3 feet higher than your intended trajectory.
Then in turn this creates bad habits with players as they emulate pro's without any understanding of what that person's doing.
In ball golf, stuff like this is like a waggle. I've seen a few video's where people make a big deal out of the "pump fake" some big arm throwers have in their swing. That's a waggle. That's not really part of the swing, its just the thing they do. Following tips like these can help, or they could have poor impacts to your game as you try and implement something into your swing that doesn't follow the basics or the flow of your dance.
And that's where things are most important, playing your game and doing your dance.
And I'll tell this, tall players are the hardest ones to give lessons to. Even being 6'3 myself, I can explain the complications of it, but the longer levers make it really hard to get people into a flow vs a compact player, especially if you're not previously athletic.
So, tldr.
X-step helps balance and flow to set your body for success when done properly.