Yes, this is absolutely part of it, and I think an underappreciated harm of LLMs is the homogeneity. Even to the extent that their writing style is adequate, it is homogeneous in a way that quickly becomes grating when you encounter LLM-generated text several times a day. That said, I think it's fair to judge LLM writing style not to be adequate for most purposes, partly because a decent human writer does a better job of consciously keeping their prose interesting by varying their wording and so forth.