Calvin already helped me find a solution to blocked dates in synced calendars. The only way to deal with this is to put on extremely high prices so that blocked dates don't show up in all calendars.
I have another issue. What if I DO want to allow guests to book over some dates that have been blocked out by a reservation in synced calendars? The only work around I have found is to 1) unsync the calendar 2) take the reservation 3) sync the calendars again.
This as only become a bigger issue for me as I've expanded my business using AirBnb. If I use the 'set price really high trick', I still have guests inquiring to stay who think it is a bug in the system.
Be aware that smart pricing also kicks in after 4 months which removes in manual overides you set. I've spoke to technical support who refund an accidental booking so obviously recognize the problem.
So in short, yes the ability to unblock automatically blocked dates in synced calendars would help, but in addition we need for manually blocked dates to NOT be blocked in short synced calendars.