[bearforcenine]

If you only have 20% of your time available to write code, then I would much rather you do not review code in which the person who wrote it had 90% or more of their time to write code. The review will be less thorough, correct, and timely than if someone else who regularly spends more time in the code.

These 'junior engineer' tasks are attractive for a manager who still wants to be in the code. They are non-critical and small. Perfect for someone with an unpredictable schedule. However, they also provide an opportunity for the manager to have a better, but still imperfect sense of the codebase and technology.

[ElBarto]

If you're a manager you don't have 20% of your time available to write code... If you want to write code then stay in a position where it is your role.