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Hi there Not a Pilot,
I hope I can be of some assistance to you regarding you question, but from my understanding some aircraft in X-Plane 11 have been updated and upgraded in some ways or others, and others like the Cessna 172 have been completely overhauled and re-designed completely.
Although I can't give you a solid answer, my suggestion would be to download the X-Plane 11 demo and when selecting the aircraft type, there is a selection box to view older aircraft from X-Plane 10, which I assume are not shown on the main menu automatically because they haven't been updated between versions at all.
Hope I helped!
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