Considering the very high volatility of crypto, I'm not sure that this is a good decision.
In my opinion, the risk is very high, especially for the poorest people.
Tether is the cryptocurrency but its value doesn't fluctuate. Being cryptocurrency alone doesn't satisfy the criteria of being volatile. Petro Coin is oil-backed coin so it will not fluctuate huge like other completely non-pegged cryptos, for example Bitcoin or Ethereum. Rather it will show behavior like fiat currencies, for example USD or Pound.
I think it is smart decision from Venezuelan government by giving free wings to country's economy via crypto but at same time limited fly with oil backing.