And I have worked 15 years at various banks as dealer and prop trader so please kindly allow me to also share another angle of the same issue: it is generally not the poor fcms or banks or brokers that get fleeced but it is he customers. And now running my own gig I understand the other guy all too well when he says he looks to keep costs down. An FCM loses NOTHING from a client who had a big mouth but traded little to nothing. A client on the other side who relies on what some guys on an anonymous forum tell him takes a lot of risk hoping an FCM may do this or that, all on the hopes of eventualities. I am very critical and outspoken Against FCMs in general because they are unnecessary middlemen, some add value above their regulatory function, others don't. But even charging opaque commission rather than offering transparent commission schedules is something I criticized for years and which adds to the mistrust people have in FCMs. Their sales men come out all the time to put a spin and great sounding story around this topic but so far none of the arguments convinced.
To sum up, if it was as you claim it is then the FCMs should have no problem to put it in writing and advertise upfront, "platform fee waived after xxxx number contracts executed in any given calendar month" or the like.
All else is misleading, disingenuous and raises all sorts of questions. There is a reason FCMs have never existed or else been disposed of in all other jurisdictions. But American "industry regulators" (cough cough) for obvious reasons stubbornly resist any change.