Power difference between flat and climbs

From friends I’ve talked to, it seems generally accepted that people are able to produce more power on climbs vs. flat ground. I’m wondering why this would be. I did an 8 minute FTP test last week on flat ground and averaged 280 watts. The next day, I did 300 watts over 10 minutes up a steep climb at a lower RPE. I felt fresher, tried harder, and was more motivated for my FTP test yet produced less watts. Any ideas?

A post was merged into an existing topic: RPE & Power on climbs vs flats