I just noticed this 2 days ago when I shared a video that I watched on the app to Discord and I noticed that the video was 50% shorter on YouTube than the one I watched on the Android app. Try searching for "Reducing rational expression to lowest terms" on the app and compare it to the one you find on YouTube (https://www.youtube.com/watch?v=7Uos1ED3KHI), you will notice that they have different durations.