One could, with as much justification, claim that someone who spends much time writing code in their free time is likely a junior or otherwise immature develope

One could, with as much justification, claim that someone who spends much time writing code in their free time is likely a junior or otherwise immature developer who still likes code for code's sake and can't be trusted to make good, efficient, solution-focused decisions that senior-level and higher developers must make, since the correct call may often be "do not write new software". I don't think that, but it's just as reasonable a position with about as much grounding in reality.