There's a bunch of pilots that pinch rather than thumb.
It probably comes from using the bigger transmitters with larger joysticks and are easier to control by pinching.
But the Sparks transmitter is so much smaller, along with the joysticks, that pinching is difficult for some and trying to manipulate the buttons well.
I think DJI designed the remote for thumbers like a game controller .
It feels comfortable and the tops of the joysticks are knurled for better grip.
I had never even considered the pinch method until I saw a YouTube video comparing the two styles. I tried it myself but it was very uncomfortable and I felt like I was paying more attention to my fingers than my Spark. It's thumbs for me.