Models are never aware of themselves as the data they are trained on doesn’t mention them - a bit of a catch-22!
“Claude 4” is not a concept on the internet when they train the model, so it’s not aware of it’s own existence, and therefore falls back to saying it is Claude 3.5, as that is a model it is aware of from it’s training data.
Rules may fix this, but it’s likely not worth adding a rule just to get it to state it’s real name - you are always talking to the model you pick in Cursor!