To the best of my understanding, flex addressing is assigned to each PHYSICAL slot on the chassis. So if you replace a server, for example, on Slot1 that new replacement will inherit the addressing assigned to Slot1. Make sense?
Yes, that is correct. FlexAddress if enabled keeps the MAC/WWN for the physical slot in the chassis and doesn't move with the blade.
More about FlexAddress (and FlexAddress Plus) can be found in the CMC Users Guide:
There is also a whitepaper available here: