[earthly10x]

When they understand the difference between software engineering and software development.

A senior software developer understands what it means to scale and align software engineers, as a unit or team. This along with understanding that the code is not what matters but rather what the algorithmic design, innovation, invention or discovery that can be done with a particular language or code (or notation in mathematics or music).

[mathgeek]

That sounds more like the difference between an engineer and a developer.

[lisivka]

Developing experience is orthogonal to engineer experience, so your statement can be reworded as "A senior developer ... junior developers ...".

Just my 5c.