Suppose I'm a retired gentleman in Ruritania with one million Ruritanian rurs in the bank. The King of Ruritania has got himself into some deep debt problems with foreign creditors due to his addiction to racing and eating greyhounds. He can either say:

a) "Guess what? I'm only going to pay back 10% of my debts! Suck it, creditors!", or

b) "Ohhhh, suuure, I'll pay back all my debts. Oh, did I mention that a Ruritanian rur henceforth has one tenth the value it used to? Heh, cool."

In the latter case my savings are completely wiped out, as are the savings of everyone else in Ruritania [while mortgageholders suddenly become very rich]. In the former case, while there'll probably be some damage to the currency my savings aren't affected so badly.

If everything in Ruritania is "worth" 10% of what it was, then nothing has changed. It's only foreign goods that have become more expensive, and your exports have become cheaper.