Interesting analysis. I think Gemini is a little confused regarding point 3. If you want to bend or warp something you need to cut/slice it. In this regard there is no difference between Flowify and ShapeBender. I suppose the confusion stems from the fact that the intersection code in ShapeBender is intermingled with the topological computations - Flowify has a distinct pipeline where intersection happens at the start.
In the example on youtube the time difference is the result of the very dense grid. The time complexity of Flowify is dominated by intersect and if you have a dense grid it will take a lot longer.
The good news is that the dense grid is not necessary. You only need a grid with vertical lines (like the first example in the video) if the source geometry is prepared properly. Flowify does not like inner face loops in the source geometry, if they are removed the simpler grid can be used. Here is a short description from another thread.