Can anyone point me to the FAA regs which say that the certificate issued on the basis of a foreign license must be "activated" by a flight review and ground review?
and knowing that will be a part of the Flight Review when it comes to ensuring your knowledge of the FAR's in the ground portion of that review.
A foreign pilot with a FAR 61.75 is no more exempt from the requirement for a FR than any regular full FAA certificate holder.
The term 'activation' is often used as you can get issued a 61.75 and stuff it into a drawer for the next 6 months. Until you complete the FR it is still not usable. Once the FR is completed and signed off in the log book - the clock then starts to tick for the next 24 months.
As an aside, if you changed address in that interim period and didn't notify the FAA - then it would still not be usable even after a successful FR.