FamilySearch Ged export only assumes biological relationships
Ex. My grandma was adopted. For almost her whole life (until about 5-10 years ago), that was all she/we knew. I had added those parents to FamilySearch with the relationship type 'Adoptive' selected for both those parents. Then later when we discovered her biological parents added them with the relationship type 'Biological'. When I imported the ged file produced by getmyancestors to Ancestry it uploaded all of these, seemingly regardless of relationship type, as biological parents showing many of my relatives with multiple choices for Bio parents. Unfortunately I can't show you an exact example for this since all examples I have are from/for living people.
I attached a redacted screenshot of the structure in FamilySearch and how it was imported to Ancestry so you can try to replicate on your end.
Yes, there's a similar issue with step parents... It duplicates the family.
Part of the problem is that each gedcom implementation handles things differently. I think I saw a note when uploaded to ancestry that it was a step parent, but what good is a note when the tree looks broken?
Perhaps we can provide support to a minimal set of common implementations, satisfying GRAMPs, Ancestry, and a Windows/macOS tool.