Short Answer: That ALL depends HOW "Old" the Record is ... and, from where
The individuals/persons, that now appear in "Family Tree" of 'FamilySearch', came from a variety of ORIGINAL (and, CURRENT) "Avenues"/"Mediums" ...
[ But, not limited to ... ]
▬ The "Temple" Department, from "Temple" Work (both, "Living"; and, "Proxy")
▬ The OLDEN Days ... "Paper Work" ... Submitted Genealogies
▬ The forerunner to "Family Tree", that being "New.FamilySearch" (Programme)
... As entered by, both, 'FamilySearch' (ie. Records Extraction); &, Users/Patrons Today ...
▬ Principally, physically input by Users/Patrons
... As, NO LONGER, 'FamilySearch' (ie. Records Extraction)
▬ or, "Uploaded" GECOM Files by Users/Patrons
That said ...
Is there a User/Name, other than just 'FamilySearch', against the People?
[ Best place to check is "Gender"; as, that is usually the ORIGINAL User/Patron ]
As an aside ...
IF, you are willing/happy to "Share" their PIDs in this (Public) Forum; THEN, if you provide that, we can have a quick look; and, most likely, give you some idea.
Here is how you may be able to determine this.
1) Go to your grandfather's detail page on a computer. In the right hand column scroll down to Latest Changes:
2) Click on Show All. This opens the Change Log which is a record of almost everything that has ever happened to his record in Family Tree and who made those changes from newest to oldest:
3) Scroll down to the very end of the list to see when the person was added to Family Tree and by who. You will run into one of two situations.
If the person was added to Family Tree by a user, you will see the date the person was added and the user who made the addition:
Click on the user's name to open a box to contact them. This particular user has included his e-mail. You will always have the option to message through FamilySearch.
At other times, when you scroll down, you will see this:
An early 2012 date and FamilySearch as the user means that this person was added to Family Tree as part of the original import of data into Family Tree when it was first created from older systems including New Family Search, the Ancestral File, the IGI and others. In this situation, there is no way to determine the original contributor of this information.
However, further up in the Change Log, if anyone has made any edits on the record, this could be the same person that put the information in originally or may be a relative you didn't know you had that you may want to contact.