I'm a recumbent rider and I've done what you say more than once, especially this time of year.

Yeah, you'll pass me on the uphill because the geometry of the bike doesn't let me get as much torque on the pedals as you can when you stand up, so I spin. Once we get to the top of the hill, though, I'm going to kick it into gear for exactly the same reasons. First, as Woodway pointed out, I've got the aerodynamic advantage, especially with my fairing. Second, because I do spin more than most DF riders, I'm going to be more efficient on the flats.

Further, I'll show you no mercy on the flats or downhill. I'm going to push it as hard and fast as I can. Why? Well, there's another hill coming up, you see, and I don't climb as well as I'd like...

Just yesterday I played tag with a DF rider for quite a while. He'd pass me on the climb, then I'd pass him, then he'd come back, etc. We had a sort of conversation going there for a while.