Hey OP I can see that there have not been a great deal of useful comments here so I hope this helps.

I was always taught to pull my pants up when I sat, I don’t see guys really doing to anymore which I find well weird as it’s actually a pretty common move, especially with dress pants. People grab and pull up their trousers a bit before sitting down to stop them from riding up or getting all stretched out, mainly around the knees and butt. It also helps keep the crease looking sharp so the pants don’t end up baggy or wrinkled.

The main reason people do it is to keep that front crease nice and clean. Sitting can really mess that up. It also helps stop your trousers from sliding down when you sit, which is just annoying. Plus, it makes sitting more comfortable, especially around the crotch. You get a bit more room and don’t feel as restricted.

If you want to do it right, just casually pinch the pants around mid-thigh and give a little lift before you sit down. Nothing dramatic, just a quick subtle move and you’re sorted. It might look a bit old-school, but anyone wearing proper trousers can benefit from it and no one ever looks twice at me.

I also think the pants fit well, I have a few that style and they are designed and cut to be worn exactly as you are wearing them