I would suspect the laminated core is for assembly reasons. There is a long history of press fitting laminations onto a shaft to assemble electric motor rotors without welding or the use of bonding adhesives, and using a solid rotor would either require a shrink fit or adhesive bonding of the shaft or machining the shaft and rotor as one integral piece from bar stock, at considerable extra expense.
While its *possible* to glue magnets on the outside of the rotor, I question its use in this case. Nickel plated magnets are known to be more difficult to glue reliably, and differential thermal expansion + most epoxy's tendency to soften at elevated temperatures, (in some cases loosing much of its strength well below the boiling point of water) make this sort of failure of a segmented magnet inrunner rotor, with no banding to provide tensile strength, far too likely. Outrunner construction would have kept the glue lines under compression, and pancake construction would have allowed the use of a substantial outer band to provide the tensile strength to retain the magnets.