A transmission is a fluid pump. What works for one fluid pump ought to work for another pumping similar fluid. Most ATF's are fairly similar, so for the sake of argument they're similar. The Magnefine has not shown to be a restriction in flow. Having two in service (one on a Honda 5-speed automatic transmission), I can't tell they're installed except by looking.
I'm not surprised a Honda dealer would refuse to install it. It's a chance they would not sell a remanufactured transmission to the OP.
I'm not surprised a Honda dealer would refuse to install it. It's a chance they would not sell a remanufactured transmission to the OP.