Generally as NCS said but some later dragged Bruce Quarrie and Phil Barker and even Newbury rules into the term which is not what the progenitors of the term had in mind I think.
Barker, well WRG back then, were the antithesis of Old School. They were all about ‘realistic’, ‘historical’, and ‘accurate’.
Quarrie and others added layers of complexity to periods other than Ancients, and don’t even get me started about the Newbury bollox.
Obvious contrarian and passive aggressive old prat, who is taken far too seriously by some and not seriously enough by others.