Hello ! I'm Aymeric, and I'm here to help !
Since the Build 22557, Microsoft has reimagined how Focus Assist work on Windows 11. It is now integrated with the Clock app, and it works with Focus sessions. It also work with the Do Not Disturb mode. You cannot disable it like before, but in the Focus settings, you can hide the taskbar timer if needed. Also, it is a totally optional experience : if you do not want to use it, you're not forced to.
If you enable a Focus session by mistake, just click on the Windows clock at the bottom-right corner of your screen and choose "End session".
Feel free to ask if you have any other question !