On dictionaries: you're the one who insisted on dictionaries, only to produce wikipedia links instead :)

Now how is it bias? Well, it's in your own answer. You are literally claiming things based on what you believe them to be, not based on what they likely are. For the latter, we'd need a longer timespan and more usage data. So you fiddled with it a bit in a timespan of a week or so and based on this tiny sample, came to a conclusion, that as you specify is your belief, but not really hard data. That is quintessentially what a bias is. Or to borrow from Mirriam-Webster again: an inclination of temperament or outlook especially : a personal and sometimes unreasoned judgment : prejudice

I assumed bias was meant to mean I'm biased towards Anthropic, or to reflect some other unfair semi-hidden agenda that influences my writing.

I do have a relevant bias here I guess: I'm biased towards the pattern of granting an LLM the ability to execute commands in a Unix-style environment. I've been a huge fan of that approach ever since ChatGPT Code Interpreter launched in early 2023 and I'm excited that skills further solidifies why that pattern is such a good bet.