You can throw away the compiler and the developer who created the software will still understand how it works. You can't say the same about someone who used an LLM who would need an LLM to continue working on the project and understand how it works. If the tool understands the code better than you and can't continue without it, you have essentially given up ownership.

The only caveat with my statement is that there are different degrees in which you can involve an LLM in your project but I mean if you are using it to write the majority of your code.