There’s a saying in the zen tradition that if you start to slouch, your mind starts to wander. I have found that to be true, but I haven’t heard anything about your hands feeling uncomfortable and the mind wandering. I think the same principle does apply.
In the Zen tradition it’s often said that you have to sit exactly like this and do exactly this to practice. There’s some diversity of thinking on this matter. I know zen teachers who say it doesn’t really matter how you sit. Some say lying down is okay and I know of one unorthodox zen teacher that advocates sitting in chairs. But, it’s normal to do the cosmic mudra—it’s the standard and traditional way to sit.
But I did something different. Because I felt like it. This seems like a minor thing and in some ways it is, but it’s part of a much larger issue.
We sometimes take our practice and put it in nice neat little containers, but it doesn’t always fit. People will tell you what the Zen way is or the Theravada way, or the Tantric way. I’ve been fortunate to meet teachers who encouraged me to find what works for me, but I’ve encountered plenty of the other kind too.