This is correct. While looking into this for a friend I came across: "for a full year, you'll earn 0.5% APY on what each person you refer deposits" [1]. Still not a pyramid scheme, since 0.5% is a small fraction of the total yield paid out, but pyramidesque.
[1] https://stablegains.zendesk.com/hc/en-us/articles/4409440197...