Funny! Bryon doesn't think it's a serial number.. even though they were 'built serially', and have a unique number assigned to each part which is a part of that 'series' of numbers. Even the original GM document refers to them as 'serial numbers', noting that the state of Georgia required unique 'serial numbers' for each of these major parts/assemblies.
Trackable? I'm sure that GM 'tracked' the serial numbers during the period it was critical to them (the warrantee period), and perhaps after. Since the purpose of the entire CE/CT documentation and serializing was for 'theft' purposes, it was probably up to the owners of the vehicles to maintain records of warranty replacement parts installed on their cars to be effective for that purpose; at least it's true for that today since we apparently don't have access to the original GM 'trackable' information.
Attached below is a copy of the original GM internal letter creating this system which refers to the identification numbers as 'serial numbers'.