You can put tape in the back or the front of the thumb hole (or the sides). You can use rough white or smooth black. There are different thicknesses for each and different "feels" for each.
You have to have something to adjust for swelling and shrinkage, unless you are a robot. Every human's extremities shrink and swell, to one degree or another ,with the seasons, with changing temperatures and humidity and with food type and amount and with age.
You can use tape or other devices in the holes or on your thumb. Not every solution is right for everyone. You should some and see what results you get.
I used to use only black smooth tape in the back or the front of the thumb hole. One day I ran out and needed some. I had never liked the feel of white tape at all, ever!!I borrowed a piece of white tape from someone and was astounded at how much I liked the feel of the white textured tape. I had always used plain medical white tape. The one I borrowed was bowling tape. What a HUGE difference it made for me. It acted like an on/off switch for allowing my thumb to exit cleanly. I've used white in the front of my thumb hole ever since.
"None are so blind as those who will not see."