Oh no, they are not. If you are day-trading or scalping (say more than 20 times a day), some futures brokers will eat a significant portion of your capital just with the negative slippage alone.
I dunno where this idea comes from. Must be from stock traders. If you do not want negative slippage, use limit orders.
That's one way to do it. In fact this so-called "latency" can bring millions of extra profits to the brokers, each year, at the expense of the retail traders... High frequency firms use a similar trick, but at warp speed.
And how exactly do you think a futures broker profits from that? You know futures are traded on a regulated exchange, right?