When combining sections into a Parent course shell using cross-list section, students are compiled into one course shell, but you have to manually click through each student's profile in order to enable that the student can only interact with students in their section. When there is over 100 students migrated into a shell, it is very time-consuming to change this setting.
When cross-listing a section, having an option to enable that students will only be able to interact with their section. Or having a setting in the Sections tab of Settings that will flip student profiles to only allow students to interact within their sections.