Old-style throw-out bearings are multi-piece assemblies. If the bearings and races are undamaged, they might just get greased and reinstalled. If they are questionable, they usually get replaced by the sealed, one-piece unit. At Max, a clutch pack comprised of diaphragm spring, pressure plate, clutch plate, housing cover and assorted screws, washers, compression ring and o-ring runs ≈$550.00 in today's dollars. A new-style one-piece clutch piston/bearing runs ≈$116.00 in today's dollars, so it seems judging from the price back then, they just greased an old-style bearing and race setup that was in good condition, but needed to replace its cup (piston). it should work ok, if that's what happened. Possibly, the new-style wasn't available.