This is a correct interpretation. Being that security is a requirement to perform the task they are paid to do, NOT a direct task they are paid to do.
For example, if you are required to pass a physical examination, you would not necessarily be paid to sit in a physicians office.
Also, you are not paid for your time driving back and forth to work, even though you are required to work at a specific place.
Correct ruling.
Let’s go a bit further. My 8 hours of sleep is required to do good at work. Should I get paid for that? No,but as long as I am not free to exit my place of employment, per requirement, I should get paid for it. This is bizarro.