As per my post-close comments on Can GEDCOM export set root person correctly? I have now identified what Reunion expects when setting the home FAMILY not person. It is set based on the first family record on the GEDCOM, not the first person.
Would it be possible to set the first family record on the GEDCOM to be the one that belongs to the ‘home’ person in RootsFinders. From my testing, this would fix the issue.