All I can say is that you must have a lot of confidence in your ability to get that applique exactly where it needs to be sewn. I don't think I could never be that accurate with placement. But then again... If I used a spray glue....maybe.
I have a couple of good, sharp applique scissors that I depend on to do the trimming job without a lot of trouble. They work well for me, even though I rarely do any embroidery these days. Mostly piecing for me and sewing on bindings.