It's complicated because FQP still owns those baby blue parcels that require Mandarin Drive extension for access.
My understanding is that any of the "owners" of the parcels can activate the building process for that road (now just Stan Thomas or Universal, before that also included the 101 acre owner Orlando IA). If Universal acquires all of the land, then they can change it entirely.
But if FQP wants to keep those baby blues, then they can actually pursue having the whole road built out based on the rights of way granted.
That's also why those FQP properties are so important. They're right in the middle of the theme park zoned properties, and they have that Mandarin Drive extension option. If Universal wants to take complete control of the Mandarin Drive extension, then they need to take over those FQP baby blue properties.