A "specification"as labelled to the consumer is from a predetermined set of international standards.Yes but surely a specification is a specification and if a certain manufacturer insists on XYZ as long as the lubrication company produces XYZ should be right
A "specification" from an equipment manufacturer to someone blending an oil for them can be an exact breakdown of all the components of the oil.
So in that regard a "specification" can mean two very different things.
An "own brand" oil can be sold (as some are) with no declared specification, but in terms of what it's actually made of it will still have a specification.