That sounds like a horrible onboarding experience. Human mentors provide a lot more than just answering questions, like providing context, comraderie or social skills, or even coping mechanisms. Starting a new job can be terrifying for juniors, and if their only friend is faceless chat bot...

You're right. We need to keep tabs on the culture for new hires for the reasons you mentioned. LLMs are really good at many onboarding tasks, but the social ones.

I think done right it is a superior onboarding experience. As a new hire, you no longer have to wait for your mentor to be available to learn some badly documented tech things. This is really empowering some of them. The lack of building human context / connections etc is real, and I don't think LLMs can meaningfully help there. Hence my skepticism for the horse analogy.