If the AI doesn't get the mechanics right, and you have subtle game-breaking bugs that make it impossible to complete, you will never be able to fix it.
I don't know about the article's studio specifically, but regarding AI game engines, I'm mostly worried you won't be able to make engine edits, or the engine will only be able to make an extremely narrow subset of games, or exiting the WYSIWYG/SaaS means starting over from scratch. If the engine targets a specific genre, it could cause a flood of low effort garbage. Some genres are already flooded because the easier game engines have tutorials and asset packs for them.
There is a non-intuitive feature of current LLMs, and that is, they are capable of refining over and over their own previous outcome. You can ask to revisit it, to improve it, check it, etc etc. use this to fix its own bugs.