After Speaking with Radykal I learned that when using the "Share Design" feature - ONLY the FPD part of the customer design is shared.
Any selections made using MSPC are not included in the shared version of the design.
This means that if you use MSPC, then when a customer shares their design (on Facebook for example) the image generated isn't what the customer designed.
I thought this was a bug but apparently not.
I'd really like to see this included in the next update as anyone who uses MSPC cannot use the "Share Design" feature of FPD!
(Wasn't sure which thread to request this so feel free to move if required).