Yes, you are correct, when you say; "Yes, this will ONLY happen IF all individuals are included."
What I have requuestd from FTM is the OPPOSITE of the EFC, or an Orphan Records Report, of all people NOT RELATED to a selected person by blood or marriage.
I have a similar situation to your cemetery situation with my surname study. My New England ancestor is the ancestor of 90% of the 15,000 or so people of that surname in my database. But there a few post-Revolutionary immigrants of that name and maybe 1,000 or so people that I believe are descendants of the New Englander, but have not been able to place them.
I can currently get those people in a separate database by
1) using the EFC with the INCLUDE Everybody in Database option UNCHECKED in a copy of my file,
2) then Right Click > Select All,
3) Right Click Export that group,
4) Right Click Delete that group.
I will be left with all of the people in my surname study not tied into the New Englander patriarch in the remaining database.
But, that would be easier if FTM just had an "Orphan Records" report, which would be the opposite of the EFC.