when you dont know which one why is there a box or chose "unknown"
If in doubt choosing living because that protects the privacy of a living individual. Then keep searching for documentation of death or wait until they are over 110 years old before marking them deceased.
On the grounds of, "Privacy", alone ...
For individuals/persons who were Born, as a general run, at least, LESS than 110 Years ago ...
Or, even, better still, who were Born LESS than 120 to 130 Years ago ...
IF, one, DOES NOT know; and, CANNOT prove, with any Record (ie. "Source"); or, "Details" (ie. be able to quote a DEATH "Reference"), that an individual/person is Dead/Deceased; THEN, one MUST have the 'Status' of that individual/person as "Living".
There have been, far TOO many occasions; even, in "Family Tree" of 'FamilySearch, when and where people who were, in fact, "Living", found THEMSELVES (or, even "Relatives") as being recorded as "Dead"/"Deceased".
The aforementioned might seem 'funny'; but, I assure everyone that, in fact, this is NOT 'funny' - this can be very disturbing.
The "Privacy" of "Living" individuals/persons is of the utmost IMPORTANCE, in fact, paramount, to 'FamilySearch'.
"Deceased" individuals/persons, in "Family Tree" of 'FamilySearch', CAN be 'seen' by ALL Users/Patrons.
"Living" individuals/persons, in "Family Tree" of 'FamilySearch', can ONLY be 'seen' by the User/Patron who "Created" them; as, they reside in the "Private Spaces" of the the User/Patron who "Created" them; and, they CANNOT be 'seen' by any OTHER User/Patrons.
IF, there was a 'Status' of 'Being' (ie. somewhere between being "Alive" or "Dead"), being the state of "Unknown", when one cannot CONFIRM Death; THEN, 'FamilySearch' CANNOT enable such individuals/persons to be 'seen' by ALL Users/Patrons. Such individuals/persons would also ONLY, be able to be 'seen' by; and, reside in the "Private Spaces", of the User/Patron who "Created" them. In such a case, WHY, even bother, to have such a 'Status'. It is now very easy for us (as individual Users/Patrons) to 'look' through the "List" of "Living" individuals/persons in our "Private Spaces" - and, work on them.
IF, one goes to one's "My Contributions"; THEN, one can 'see' a "List" of ALL the "Living" individuals/persons in one's "Private Spaces".
Here is the direct 'link' (ie. URL), to the "List", of "Living" individuals/persons in one's "Private Spaces", under one's "My Contributions":
Here are some "Knowledge Articles" in 'FamilySearch":
I hope this helps.