Well, in that case we just have another example of someone on the support staff writing something false. I personally think they're just driven to close tickets, not to solve problems. Replies like this are intended to dismiss your issue. That's frustrating.
I'm surprised to read that you're able to import a GEDCOM from Legacy without issues. Are you sure it's not dropping data? (Perhaps that doesn't matter if your main db is in Legacy.)
I'm with silverfox. They need someone capable to look at this code and fix it. For blood relationships, this is very easy to do. I assume that FTM's database is an SQL variant, which means that they probably used a closure table or some similar method to store hierarchical relationships. If that's the case, a simple query of the data will return all blood relations in an instant. (It's the by marriage relations that are more difficult.)