Not everyone sets seams the same way. The mother of one of my friends sewed the clothing for her 4 girls as they were growing up. She set her seam by running the fabric through her fingers, with fingers on either side of the seam. it worked for her and still works for her daughter. A different way to finger press.

I think you can see the difference in the thread after you set your seam, the thread just melds into the fabric, then when I press the seam it lays a lot flatter.

My Mom first showed me how to make a quilt top, she never had time to quilt them and finish them up. She didn't even iron, or press the seams. This was over 47 years ago. As I bought quilting magazines and books I learned about pressing but, they did not cover setting the seams. I'm not saying all, just the ones I had. A lot of the ways things are done now are different than how they were done early on.