Afaik you have posted two vids connected with locks. One shows Amaral opening the front door of 5A from inside. The other shows the cleaner opening the door inside her own home and the lock is completely different from 5A.
I'm sorry to say you are wrong on both accounts.
There are two videos of interviews with cleaning staff and restaurant staff and the locks in both videos are exactly the same as that in 5A.
The other one Alexandre Simas knocks on the door of 5A and GA opens the door from the inside. We never see them use the key.
Surely the primary function of the knob is to disengage the snib from the inside.
We are talking about a knob, but in fact it is only a type of knob. In fact it was a type of hook that you can pull to "to disengage the snib from the inside".
To describe the parts of a lock is rather difficult for each component has its own technical term, that I'm not particularly familiar with.
But "snib" I think is termed the "latch bolt" but it might also be spring loaded bevelled latch bolt.
But what is also important is to understand the function of the latch bolt locking device. Did they move together or were they moving separately? Obviously pulling the latch bolt hook this withdrew both the latch bolt and the latch bolt locking device so the door can be opened or closed from the inside.
What has never been demonstrated is that the door would just shut without a key or without pulling on the hook.