There are many things that I don’t fully understand (especially in the deep and detailed area of colour profiles and colour mixing) but I generally assume they are there for a reason. The best way to figure them out is to play with them or ask about them here on the forum where experienced users and also developers hang around (when they have free time).
As for the Cage Transform granularity, I can’t understand what it does either but that may depend on the type of image that is being transformed e.g. lineart vs a photograph.
Until I watched your video, I didn’t know that you could select multiple Warp anchor points and move/rotate them as a set, so I’ve learned from you. Your tutorial videos do work well 
Here is my merciless criticism of the Selection Tools video. Two points:
- Explanation of selection Action.
At the end of this video, you presented and explained all the selection tool Actions. I think this would have been better done at an early stage.
When you demonstrated making simple selections, the Action was set to Replace. At 5:13 with the dog, you select a single region with Action set to Replace, then at 5:26 the view switches to a canvas only presentation of the dog and you select both eyes for moving. For this you must have changed the Action to Add but did not explain that.
Any beginner trying to follow the tutorial by pausing the video and copying what you showed would have not been able to select both eyes. That would result in confusion and frustration.
Selection of multiple regions continues throughout the video.
At 6:47, you do show the Tool Options docker with Action set to Add but it has been moved further down the screen and I can’t understand how that happened. Later on, the Tool Options docker is back to being as it was at the start.
(I realise that the video would have been recorded over several days and you may have changed workspace for whatever reason during this time.)
- Use of the word ‘scroll’.
Throughout the video, you use the word ‘scroll’ to describe selecting an option from a menu list. This is not ‘scrolling’. Scrolling is about revealing content that is above the top or below the bottom of a list window and is done by rotating the mouse wheel or by click-dragging on the scroll-bar at the side of the window.
A good example of this is the Brush Presets docker where you have to scroll through them to see all of them.
End of merciless criticism.
You didn’t cover the difference between Raster selection and Vector selection and all the other wonderful things you can do with selections but that would have been far too much to fit into one video.
Maybe do those in a future and more advanced tutorial?
I’ll post another reply in this topic with my merciless criticism of your Free Transform Tool video, only two small points there 
Regards
Ahab