No idea lol, it's just that people on here associate the placing of the lock with the cab being finished, and it my case it certainly wasn't placed until the first order was provisioned
The people who provision lines at a subscriber's house will not have any access to the FTTC cabinet; AFAIK they are two separate pools of engineers - or certainly used to be. When FTTC is installed, the engineer only makes changes (involving the tie cables) in the PCP cabinet.
Provision of the new lock might well be one of the steps of on-site commissioning that goes on before a cabinet goes live, but I have to admit that in 4 years of watching this rollout, I haven't seen a single silver lock.