I don't think this holds because we're talking about developers who know how to use a package manager, on a piece of software you have to install anyways. The friction of "uv add $other_llm_software" is too low for it to have a real impact.
I think they're more into the extra context they can build for the LLM with ruff/ty.
until "uv add $openai_competitor" mysteriously breaks in odd, difficult to troubleshoot ways.