Getting laid off and shown the door immediately after (plus having your access to systems and buildings revoked) is very common.

The reason for this is because the HR person drafting this policy probably had someone take advantage of the window between when someone is told they are laid off and when they are actually terminated, and so the policy gets made to reduce that liability. It sucks for the 90% of people who wouldn't do anything, but that's how it works. Imagine getting told you're your laid off, then your laptop handed in before you even leave the meeting room, then a security guard or HR person escorts you to your desk to pack your things in a box before they walk you out the building.

Mind you, you'd probably still get some severance bonus or keep getting paid for weeks or months, but you just wouldn't be expected (or able) to work.