I first saw this in some marketing in my email, followed up and here I found the full statement:
"The new and FREE MIR Pro update patch of RoomPack 6 – Synchron Stage Vienna adds masterfully crafted MIRx presets to all instruments,"
It does not, not through itself. There is something missing here (even if it's my understanding is incorrect, eg., 'to all instruments' means something I am not grasping); I'm supposing this is predicated upon having a license for something MIRx bundle (which does not have any Synchron Stage), as the error is "check that your MIRx licenses are available on your key (venue data/Directory Manager)".
But as stated on the Products/Software/MIR Pro page, pasted above, it makes no sense to me.
I have licenses for RoomPacks 5 & 6. It doesn't make sense for me to acquire the rooms in the MIRx bundle. It would be nice to have Synchron in VI Pro rather than use up one of my 24 slots. Maybe this means only MIR Pro full, but some information is omitted from this assertion.