Exactly. If they can’t or won’t pay what they owe when it is due - that’s default. If they negotiate different terms with their debtors, technically that’s not default. If they impose the terms on debtors who do not agree, that default and a benefit of being sovereign.
I wonder what the legal ramifications are. If I take the Greek government to court in Berlin over my Greek T-bill, I bet the German court will say “Take it up in Athens instead”. Thus, debtors are incentivized to compromise. The resulting credit rating and interest costs if the Greeks don’t at least try to accomodate the vast majority of debtors is what incentivizes the Greek government. It’s a big dance… til the music stops.