That explanation is not correct. Algorithmic stablecoins rely on a pairing with another crypto, in UST’s case LUNA. 1 UST can always be swapped to $1 US dollar of LUNA. It is interchangable, so $1 US dollar’s worth of LUNA can also be swapped for 1 UST. Hence, the “algorithmic” in the name. This way traders are always incentivized to keep the price of UST at $1.

There is no collateral requirement. In UST/LUNA’s case they had collateral, mostly in Bitcoin, in the Luna Reserve Guard but their collateral proved insufficient. Some algorithmic stablecoins are entirely uncollateralized.