Uniswap takes 0.3% of every transaction, and the price depends on the spread (difference buy-sell price).

The article misses the underlying ETH-USDx pricing of all tokens on Ethereum blockchain.

The problem is not the Uniswap but the movement of ETH-USDx pricing.

For details please check - https://medium.com/the-capital/the-danger-in-the-stable-coins-thought-experiments-and-the-real-price-of-bitcoin-6042adecb0d?source=friends_link&sk=1720a20e3a2c0db2c3d85c0295ebf313