Because when you have your own rack you can put arbitrary devices and safeguards into and on it. So you're right - the datacenter can open and close and tamper

Because when you have your own rack you can put arbitrary devices and safeguards into and on it. So you're right - the datacenter can open and close and tamper with the rack as they see fit - but I can notify myself of that and even video record it. Interruption of the physical monitoring would be itself a signal. I've never done this, but I have placed many strange and arbitrary devices within, and on top of, racks I have leased and nobody notices or cares unless you're a nuisance somehow.