[Nasrudith]

Slacking is also a matter of motivation or the lack of it essentially, whether the "slacking" is a conscious act or not.

A "universal" 10x developer would be fairly rare to mythic even if restricted to a single complete subdomain like say Backend or Embedded development.

Well unless you had a massive skill discrepancy like say a team of a class of middle schoolers and a 10 year veteran software engineer but that would be a pedantic edge case like comparing the foot speed of a centarian and Usain Bolt. Technically a valid measurement of range but not generally useful.