Sorry, that's incorrect information. I've been to several countries that have pegged their currency to USD or to (long time ago) Deutsche Marks, without every claiming to the same currency in reserve. It leads to currency black markets, but it's possible to do and many countries have done it in the past.

I mean, even China had a currency peg not too long ago. It was an enforced exchange rate, nothing more. No explicit reserve backing it up.

Not in the cryptocurrency field. In this field pegging has a precise meaning.