I meant that there has to be two FRR rates. One for receive swap, one for offer swap. It sounded like you thought the option to use FRR rates for receive swap means that, when disabled, and chosing a rate that is higher than FRR on the swap offers orderbook, that you can clear this orderbook without taking the FRR-rate swaps.
Pretty sure FRR is always just one rate, for both offering and receiving funds. Or are you saying there
ought to be two rates?
Problem would be that if you create a difference between the rate being paid and the rate being received, either Bitfinex would be stealing the difference (if the rate paid by traders is lower than the rate received by lenders) or there would be a shortfall in the funds collected and Bitfinex would have to pay to cover the difference and bring it up to the rate the lenders expect to receive (if the rate received is higher than the rate paid)
I dont see a reason for that option existing. In fact its unfair to those offering at FRR. Why give them an disadvantage against normal orders? Is there a reason that explains this?
Fixed and variable rates aren't strictly comparable; you can't say with certainty that one is a "better rate" than the other because the variable rate could change at any time. A situation can be imagined where you would want to lock in a fixed rate that's slightly higher than the FRR at that moment, in case the FRR rises in the near future. That doesn't really explain why anyone would choose to take a 0.7% fixed rate over a 0.1% variable rate, but it does explain why the option exists to choose to not take variable-rate swaps.