Two years from frame manufacture to assembly sounds normal to me. On old old bikes you will find all sorts of anachronisms. Stuff used to sit in inventory for years and years.

To my eyes the Nuovo derailleur looks much too new. I look at the bike and see 50s even though I know it is more likely 60s. I would build this with Gran Sport mechs. But could Nuovo be used? Sure. Could Nuovo be correct? Yes.