I think you're being a little harsh on those who take this gif at face value. I saw the video that it was made from on some purportedly reliable news show. This is why I don't trust any news from the so called established media, because of course that video is a fake, with one good piece of evidence being what you point out about the Stretch Armstrong move by the soldier.
So just to be clear, your point is that the video is a fake (yes) but also that he didn't go the Tomb of the Unknowns at Arlington? (as evidenced by your question, that follows)
"If this was for Veteran's Day, why is it taking place at the Tomb of the Unknown Soldier? Veteran's Day is for the living."
Why aren't you asking Demented Joe this question? He's the one who went there on Veteran's Day. The image I attached is from the following AP news story.
https://apnews.com/article/biden-veterans-day-arlington-national-cemetery-e348db2729df096a1d69fdc550501d60
I know, it's a total risk to trust an AP news story, so I'm exposed. But I think I saw it reported from a number of media sources, of varying political viewpoints, that he did go there on Veteran's Day. Isn't it sad that we have to take the political viewpoint into account when determining the veracity of what is presented as a "news" story?
Overall, I have to give Demented Joe credit for a decent performance. Distracted at times? Yes, but at least he didn't keep looking at his watch. Wobbly in his stance? Yes, but to be fair (something you never hear libs say) it looks a bit breezy there, and at his age, a strong breeze is a dangerous thing. And he did make it through the ceremony without too much help from others. So all in all, not bad from our Demented POTUS.
