Tesla, in their infinite wisdom, has decided to prioritize charging over cost.
I have a wide charging window too…. I just set it to start charging at the beginning of the window. It’s always done by the end. If I get home during the window and decide to plug in, I just stop charging or I set the battery limit to match the remaining hours of the charge window.
Not great, but it works. I do have a teslafi rule set to “if plugged in at home and charging at the end of the charge window stop charging and notify me” as a backup. It’s only triggered very rarely.