The LLM-generated code is by far the worst technical debt. And a fair bit of that time is spent debugging subtle issues where it doesn't quite do what was prompted.
Having to write all the specs and tests just right so you can regenerate the code until you get the desired output just sounds like an expensive version of the infinite monkey theorem, but with LLMs instead of monkeys.
I use LLMs to generate tests as well, but sometimes the tests are also buggy. As any competent dev knows, writing high-quality tests generally takes more time than writing the original code.
There's an interesting aspect to the LLM debt being taken on though in that I'm sure some are taking it on now in the bet/hopes that further advancements in LLMs will make it more easily addressable in the future before it is a real problem.