That’s a very academic viewpoint. People initialize variables with defaults, and sometimes, that default needs to be an empty list. They are just holding it wrong, right?
Most people writing any language without a linter are holding it wrong.
When a linter warns me about such an expression, it usually means that even if it doesn't blow up, it increases the cognitive load for anyone reviewing or maintaining the code (including future me). And I'm not religious — if I can't easily rewrite the expression in an obviously safe way, I just concede that its safety is not 100% obvious and add a nolint comment with explanation.
My point was that no matter the conceptual purity or implementation elegance, if a language design decision leads to most people getting it wrong–then that's a bad decision.
But it's not about that. I don't like this decision either, but the other side of the trade-off is not just about some abstract concepts or implementation, it's about complexity of the model you need to keep in your head to know what will a piece of code do. And this has always been a priority for Python.