Is this a standard approach to solo role playing?
It is one approach, and goes back to a long time ago with choose your own adventure books.
There are other, less on rails approaches, where you play an RPG and replace what usually would be GM decisions by random tables (concrete and inspirational) and mechanics that introduce complications and challenges.
I'm not really surprised - these are LLMs = Large Language Models. They are made to remix natural language sources, they can walk like a duck and quack like a duck. But the things that are really hard to get right with them are math, logic & reasoning, and facts. E.g. https://www.forbes.com/sites/johnwerner/2024/10/07/ai-is-usually-bad-at-math-heres-what-will-happen-if-it-gets-better/
AI image generators are even worse, e.g. https://gpt.gekko.de/ai-numeracy-text-image-models/