And yet even that one gave me a 22.5mph at my wattage in the drops, not including my aerobars. I don't think my powermeter is in error just based on what I see from other powermeter users in my weight bracket on hill climbs on strava, but anything is possible. I use a garmin edge set to autocalibrate with the powertap , and I wasn't aware there was any way for it to read high. I thought the failure mode for these was low readings. Is that not the case?
Either 1) your power meter is off; or 2) you're a parachute; or 3) it was windier than you thought. Or maybe all three. Check your PM, then check your CdA. If your PM is reading right and the wind really was negligible then .44 m^2 for CdA while on the aerobars means you're a parachute. That's street clothes on bar tops of commuter bike territory.