In my opinion, stable coins are one of the most dangerous and shady assets that you can put your wealth in.
Firstly, stable coins represent fiat currency which is in itself something that has been historically depreciative.
Secondly, stable coins are not even actual fiat currency. There is no way the majority of the time for the investor to be 100% sure that the company issuing stable coins have completely full reserve all the time. And even if they can, there is no way of guaranteeing that the company will be willing to redeem their stable coins for fiat on demand.
So you're absolutely right. In certain instances of fractional reserve being used in stable coin issuance, which I believe is extremely probable for the majority of centralized stable coins, it is essentially no different than printing money out of thin air. It's only because stable coins are perceived to be backed fully and redeemable at all times does it have any value. But in reality, it's probably nothing like that.
This is a big problem with those coins, instead of trusting the government and their fiat now you are trusting a third party company that is holding enough currency in reserve for each unit of their cryptocurrency they print, so now you are in an even worse position than those that are only holding fiat because now you need to trust not only the government but also the people behind that coin, I know that those that created those coins are trying to give investors an easy way to transfer their cryptocurrencies to an asset similar to fiat.
But they are creating just another liability and a false sense of security among people, so for those that want to get out of the market for some reason make sure you get fiat and not one of those coins.