There is an update on support topic for 12th/13th gen CPUs and Cubase based on 2023-08-28:
Update 2023-08-28: Recent tests indicated that the situation has improved significantly and feedback from the user base supports the results. While we are still working on optimized versions of Cubase and Nuendo, the behavior running on the latest Cubase/Nuendo 12 and Windows 11 builds is mostly as expected.