I really don't understand why this happening. If someone wants to buy a product that already exists why not let them? Mixing different libraries is always a challenge. So for sure there are many people who need additional instruments when they already have several from the VI series and don't want to mix them with other libraries even if the synchronized series has the same sample base. And what about the libs that don't exist in the synchronized series? Orchestral, ... And upgade to synchronized series difficult because the packages are different. Have to buy solo violin2 too when upgrading solo strings without need.
And it can't be too difficult to make sure the instruments pro player works with the latest OS. At least for windows.