When you direct order flow to your wholly owned subsidiary you're benefiting from order flow! Perhaps pedantically you're not getting "paid" unless TH makes internal transfer payments to IB, but whatever conflicts of interest arise from directed order flow happen with the IB/TH combination the same as any other broker who's getting paid for order flow. In some cases you could say it's worse, for example guess who's on the other side of all the wide market orders when IB auto-liquidates customer's positions?