@paul_fynn I just did some testing because I was curious about this, and it appears that within our instance students are not able to see the content within the assignment except the title of it until the unlock date. It presents students with a message that says "This assignment is locked until: (date/time)". After the assignment is locked, the same message appears, however it says "This assignment was locked on: (date/time)", and students are only able to see their assignment submissions and comments, however they are unable to view the content themselves.
This could vary based off of institution to institution, based off of how things are set-up, however this is what our school has it set up as. We are primarily using the browser, at least during the school day. Students generally use the app for when they're not in school, and they're checking announcements or grades, or the like. Students for the most part will not use their mobile devices during the school day to complete assignments.