Not true. Think about how the vast majority of people are trading right now using BTC or ETH as the go between when wanting to say, go from STEEM into ADA or vice versa. They look at the current prices of each currency in USD then use a calculator to figure out how much to offer in each leg of the trade. The same will happen with atomic swaps, which are coming, and will be revolutionary in the crypto world. You just will do one set of calculations instead of two.