Exactly, so if someone could settle FX trades in one day instead of two, the profit opportunity would suddenly exist. The problem here is perceptual. Additional research suggests that something like 98% of FX transactions pass through the CLS system. That means that Steve's firm (or all the banks that IB uses to route their FX trades) is not only profiting from the spread and commission they advertise, but also the difference between the settlement time they provide to their customers, and the <i>actual</i> time it takes to settle FX trades. Trade settlement isn't a physical property of the world - it is a convention adopted by market participants. Trade settlement in equities began to accelerate as soon a equity trading was opened up to individual investors. FX is still in its first decade of general availability to individual investors, so it is reasonable to expect that settlement times will tighten up in the coming decade. Perhaps at this date, the only entity that could gain access to faster settlement <i>today</i> is an extremely large hedge fund.
If settlement moved to T or T+1, then the FX cross-rates would be priced accordingly. No-one's going to hand-out blank cheques whether you're Joe Public or Mega-hedge fund. If you don't believe the advice that you are getting, then feel free to try it. Many brokers would be glad of the commissions.