That is correct. Since this is designed to trade rather do portfolio management, it does trade in and out of one pair.
There is an FAQ here that explains the reason: https://crypto-ml.com/auto-trade/#Frequently_Asked_Questions
I have copied some of the answer here for ease:
When the first “buy” order is initiated, all available fiat (e.g. USD) will be used to purchase your selected cryptocurrency. For example, if you have the BTC/USD pair selected, Auto Trade will use your entire USD balance to buy BTC.
Likewise, if a “sell” order is initiated, Auto Trade will sell all funds stored within that crypto. For example, if you have the BTC/USD pair selected, Auto Trade will sell your entire BTC balance for USD.
As such, you should create an account specifically for Auto Trade and only put in as much money as your particular risk profile allows. Do not ever invest more than you can afford to lose.