Owners Manuals are different from Chassis & Body FSMs.
Owners Manuals were generally automatically left in the glovebox of a vehicle when it was sold new by a dealer. They give basic information like oil specs and quantities, tyre pressures, the function of all the dash switches/controls, etc.
On the other hand Factory Service Manuals had to be purchased separately and were generally only purchased by repair workshops or individuals who like to do their own repairs. (They of course contain the detailed information on overhaul procedures and specifications .... as well as some further stuff on regular-maintenance.