Inspired by what you found out I wanted to know how far I could push a planet's output using your method and if it's viable for the higher difficulty levels.
This is my homeworld at Turn 178:
I focused absolutely everything on the planet (all citizens, asteroid mines, ...) and built 20 fully maxed economic starbases around it.
Game was on Genius difficulty, Gigantic spiral galaxy, 15 opponents, Vigilant Engineers as racial traits.
Game was pretty easy, overloading the planet makes it scale very nicely with the game's progression. So this is absolutely a competitive strategy for the higher difficulty levels. I'm sure I could have pulled it off on Incredible, dunno about Godlike.
Is it cheesy? Absolutely. Is it OP? Probably yes, but mostly because there is no limit here. You can always train another Celebrity which increases the planet's approval and enables you to ship more population to it. This requires a lot of dedication and quite a bit of micromanagement though.