schneeland
Hero
I don't think so. And old-school and OSR are not the same thing, the latter being something that originated specifically in a D&D context.You're conflating retroclones with OSR, even though you start off with a definition that in no way impacts any of your bullet points. (Also, there are unified resolution systems in old school games. Traveller had/has one. RuneQuest had/has one. I seem to recall hearing that Tunnels & Trolls has one.)
What I tried to imply, but maybe didn't get through: even in newer OSR titles like Cairn, Knave, Black Hack, etc. you find some typical design elements (in particular: focus on player not character skill) in a cleaner fashion that you do in Shadowdark.
Also, I thought I made it clear enough that nothing on the list implies that Shadowdark is a bad game. I just don't think, OSR is the right label for it.