As someone who popped a bone into those ligaments a few years ago (dislocated thumb at the wrist) this is similar to a stretch I do since then.
Thumb on top of my fingers (like a fist with the thumb scooted to the top) and slow smooth movements to the edge of the range of motion. Don’t stretch to pain but to where tension starts. Which will be BEFORE pain.
I would recommend against following this image for sure, it looks dangerous