How is the security of the new telebank ensured?

Question

Browsers

The new version of VTB24 Internet Bank does not allow you to work in more than one browser tab, as was possible in the old version. Technical support declared this as an intentional innovation and explained it with security requirements.
Does the ban on opening more than one window in the browser when working with Internet banking really increase the security of the system? What is it expressed in? What dangers can lurk when using multiple tabs?