It's a payment of sats to open the door. 
Discussion
Then the device was wrongfully designed. You can do that with a simply LN-auth.
what if the purpose is to charge an entry fee?
That video is 2 years old, is from PlebLab Austin. They were doing some tests with Lnbits bitcoin switches.
I think they put it to the door just as an exper:ment. It doesn't make sense to charge your own tenants an entry each time you pass that door.
By definition a tenant will be charged for using the space.
I think keeping sats flowing into the direction of the owner of the door is a good thing. It's also a signal that the person can enter and is a member of the club.
It also shows that micro payments are practical and as Bitcoin increases in value those payments are essentially mining the foot traffic.
Keeping the sats flowing means that they are keys to entry for anyone buying a small amount. It's useful.