We actually can't judge this without really looking at outcomes.
If the parent leans on the hard earned skills to make better decisions that improves outcomes for their team and by extension the org, then it's entirely possible it makes them a better manager.
Where it gets complicated is questions non-related to this:
- Who and how is anyone measuring outcomes? This is often very difficult in abstract.
- Is the org actually setup to allow these teams to flourish? Will the measurement be fair, or is there effectively internal sabotage?
- What's the reward for being better? Would the parents life actually be materially better for making the effort?
Personally, I agree with the parent. On average, having good ICs making your IC decisions lead to better outcomes. Where there's grey areas is there's more than 1 way to structure this. Player managers are definitely valid. Better than non-technical managers with good soft skills making poor engineering decisions over and over.
Where I'd disagree is the continuous effort. Once you've reached a certain level, a lot of what happens below syntax. Occasionally you end up managing something you don't understand with contention in the team.
At this point, you either invest or defer. The problem with the latter, in my experience, is very few devs have experience with commercials, so most of the arguments are based on laziness, interests, or purism, rather than outcomes.
For the record, whilst there's managers we like working for, if they're not able to extract reward for business outcome for the few that chase that, are they actually any good?