This is not an LLM problem.

This is a people using LLMs when they should use authoritative resources problem.

If an LLM were to tell you that your slab's rebar layout should match a certain configuration and you believe it, well, don't be surprised when the cranks are all in the wrong places and your cantilevers collapse.

The idea that anyone would use an LLM to determine something as important as a building's specifications seems like patent lunacy. It's the same for any other endeavor where accuracy is valued.