Based on a comment on the Scott & Jimmo deep-dive stream, private constants get treated different and use less space in the .mpy file because of not having to store the name of the constant.
CircuitPython 6 MPY
Before 6595 bytes
After 6113 bytes
Saving 482 bytes
CircuitPython 7 MPY
Before 3671 bytes
After 3234 bytes
Saving 437 bytes
Based on a comment on the Scott & Jimmo deep-dive stream, private constants get treated different and use less space in the .mpy file because of not having to store the name of the constant.