Why do you think this is a flawed decision to do so ? In my opinion this is a conscious choice by Selig both times and a good one.
There are business models where venture funding is unsuitable as there will never be hockey stick growth or unit economics or competitive moats etc, traditionally companies usually small operate here, they are not startups, just SMB doing non flashy stuff.
Similarly also many business models unsuitable talented product teams to risk on , that are perfect for a highly talented freelancer such as Christian Selig - like third party API dependent ideas.
He is amongst the best indie developers in the Apple ecosystem and doesn't have to worry about competition quality too much in these ideas.
These are four main ways that I know of, to be a professional talented product developer -
1. Become a founder, raise funding, chase growth and do things you don't really like anymore
2. Freelance and do boring consulting work, trying to keep customer happy
3. Work in a big bureaucratic tech company and be frustrated constantly with everything from politics to red tape.
4. Pour your heart and soul into a early stage startup and watch it either outgrow you or crash and burn.
He instead gets to build products at a massive scale without having any overhead of an organization, and also making decent amount of money (upwards of few million/year with Apollo), what more can a developer aspire for ?