x_rotation seems to behave like y_rotation

The bug

The selector argument x_rotation seems to behave like y_rotation.

How to reproduce

1. Setup two repeating command blocks with the following commands

   /execute as @a[x_rotation=0..90] run say x
   /execute as @a[y_rotation=0..90] run say y
   

2. Look down
   → Both "x" and "y" is written to chat
3. Look up and rotate southwest or just spin
   → Nothing is written to chat