Probably realistic for most use cases. Scrolling webpages, writing documents and emails uses less resources than video. Unless you're watching 8 hours of YouTube a day.
I disagree. If the video decode is properly offloaded to hardware, then video playback, particularly local video playback (as opposed to streamed video) should be one of the
least taxing use-cases for a laptop. CPU usage should be close to nothing and there should just be a constant, light load on the GPU decode engine. How warm does your phone get after an hour of video playback? It shouldn't be warm at all.
Webpages, on the other hand, particularly ad-invested ones, involve burst workloads where the SOC will boost high and sacrifice efficiency to shave tens of milliseconds off the time it takes to render the page.
Word and email - I agree with you there, that's very low power use.
Is this a new battery test methodology from TomsHardware? Hence the lack of comparison data? If so, some more details would be helpful. Is it a local video file playback or online? What software/browser are you using for playback? Why? Have you tested other alternatives?