It certainly was a bias in this case - I asked for a feature, mentioning to give me popular libraries in this space, then it started coding up a bespoke solution that included among other things, a custom HTML parser. Then asked to really consider using a library for the whole thing and it 'compromised' by pulling in a HTML parser, but still keeping its own implementation.

This is just a singular example, but I'be noticed a strong and beyond reasonable bias for this from multiple LLMs (like not using the already included dependency)