Can Stashaway sell your units without your authorization?

I just started my monthly RSP with Stashaway during the March drop. I set the auto deductionon the 12th of every month. However, last week I noticed that while my money was injected to buy new units, there was also a small sell order for 2 ETFs that I did not authorize for. Upon calling them to enquire, they told me this is normal and part of the process of buying fractional shares where sometimes in order to fulfil a withdrawal order, they randomly pick users to sell small units to fulfil