I’m a civil engineer (structural), licensed in New York. Worked on the World Trade Center before (kinda trivial but the work we do) and after 9/11.
I would agree, the leaning of the building does indeed introduce a “secondary moment” as such, now just 6 inches at the top it’s probably still neglegable, but concerning.
I use to do a lot of work on steel transmission towers, hand analysis and computer analysis. Until that building approached about a 9 degree tilt, the secondary moment is arguably neglegable. NOBOBY will in that building when it’s tilting 9 degrees.
You might enjoy this link ... though it's probably trivial to you if you're a structural guy. LOL.
Simulated Structural Collapses
What's interesting about this is that these stacked block structures would tend to be more likely to retain their shape while collapsing than a typical building would -- since they all see to be constructed uniformly without any consideration for open space in the interior. And yet they all seem to have minimal tendencies to topple, as opposed to collapsing downward.
The segment that starts around the 4:00 mark is a good example, because it looks like the whole right side is going to maintain its form and topple straight to the right. But it fails to maintain its form, in a manner consistent with all the other similar scenarios in the video: the bottom of the structure separates from the top because the top can't maintain the same rotational speed.
Fascinating!