I think it's written that way because the instructions are meant to work on Windows too. But it still doesn't make much sense. I think just saying "Install CMake" and letting the agent figure it out for the current environment would be a much better approach.

Also, I think the model they were using was working with outdated data. Why specifically require Java 21 when Java 25 is the latest LTS? And furthermore, why even link to a specific JDK implementation when it surely works with almost any implementation? Probably just makes the agent install the Temurin implementation even if the system already had a working java.

My point being if the author's idea is to let AI handle the installation to avoid writing environment-specific instructions, it shouldn't then have these hardcoded assumptions about the environment. So yeah, it seems they (and the AI that wrote it) didn't really know what they were doing.