Maybe but my impression is that most of the attacks are independent of separation.
The key point is:
able to trick phones with those vulnerable 5G basebands into connecting to a fake base station
That opens up any phone to surveillance of call and text metadata and the injection of fake calls and texts and the surveillance of call and text content.
The article also says:
directing the victim’s phone to a malicious website, the hacker could trick the victim into providing their credentials on a fake Gmail or Facebook login page, for example
which seems a doubtful claim. Yes, malicious direction is always possible in this scenario but the host should detect an incorrect certificate. For sure, any insecure sessions (using any protocol, with any host on the internet) can be surveilled and can be tampered with.
One thing that I wondered about is whether the typical affected baseband processor supports FOTA and, if so, whether that can be compromised by this vulnerability - because that would open up a whole extra load of nasties.
