Exactly: they are basically fiat. What is the point? And they are only "stable" in fiat terms. In bitcoin (or gold/silver etc) terms they will be losing purchasing power at the rate of inflation.
Has anyone used the term PBDC (private bank digital currency) yet? Maybe that wouldn't be the correct term considering that the companies behind these coins aren't banks, but they do practically the same thing as any central bank - they literally issue tokens without even having to prove that they are backed by anything.
If you ask me, most of these so-called stablecoins are actually experiments being done by governments through their shell companies to one day make the transition to CBDC easier.