Good question. There are a few reasons I prefer to switch my stance.
First, I’d like to note that if I had entered my tie up with my right foot forward, I would have stayed there in the tie. I like to have the same leg forward as my collar tie push hand.
I feel more balanced if I am pushing my opponent with my right hand collar tie with my left leg back. It also give me more power because when I push, I like to have my back foot slightly at an angle so I can push off the inside of my foot. Also, it helps to have your collar tie and lead leg the same (in this case right collar tie and right lead leg) because it’s easier to fire off fakes and attacks instead of having to switch your stance right before you shoot.