1 hour indoor vs 6 hour century? Ok, I’ll look even though Strava is the worst at power graphing and scaling…
Outside 6 hour century, randomly zoomed into about 8 minutes, looks pretty natural:
And inside:
Kinda looks like erg and little ring, possibly a little too smooth (unnatural), but average power is only 85% of the graph above.
Ok, here are some graphs where I made sure the average watts are about the same, and set the y-axis to use the same range:
Those are also about 7 or 8 minute windows.
Inside and outside look about the same, and the power standard deviation around average is 15-21 watts.
From one of many posts I made on the topic: Stages power meter "jumpy" - #13 by bbarrera
My first guess, even with the Strava handicap, is that you are comparing unnaturally smooth power to outside power. But it could be something else, hard to say when Strava does the graphing and you can’t run basic statistics.
Hope that helps.