Public debt is a promise to fund future obligations and things like pensions would be significantly devalued if it isn't honoured, so in political practice it i

Public debt is a promise to fund future obligations and things like pensions would be significantly devalued if it isn't honoured, so in political practice it is debt. That debts and savings are two sides of the same coin is tautological and doesn't require a state or fiat currency. Your current account with the bank is a debt the bank owes you. All savings are debts.