I think your confusing some terms here...
A "shortblock" is a complete motor. Cases,crank, cylinders, pistons, heads, valves, waterpump. Basically, a complete motor with all the bolt on accessories removed.
"rebuilt" means that they reused/refinished the non-moving, typically non-wear hard parts, like the cases, cylinders, head. But replaced the wear items, like the pistons, rings, cams, valves, waterpump, crank, bearings and seals.
A properly rebuilt motor with all OEM parts is better than the used 5k mile motor that broke.
Sent from my iPhone using Tapatalk