Nice article, which presents all the relevant information very well.
When I learn from my teachers they often teach a basic form and then add bells after the fact. It seems pretty obvious that the forms are intended to be the same order of moves more or less, and are essentially the same form but people do things very differently. Let us separate immediately what I call 'cheating' out of the form, I don't mean it in a negative way but very often people will perform the moves in a very quick or easy manner, we cannot always perform the 100% form even if we hold it in our mind. You will see a lot of people doing this and there is nothing wrong with it but for example do you lift your leg up before six sealing four closing? Some do and some don't. Another 'example' is do you lift your left leg up in the first move or just slide it out (krebs, I saw you lift it up in the video). We don't do that. It's not important. But the idea is there is a level of difficulty added in to the exact same moves.
So separating out this kind of bell which is added to the form, the forms are pretty much the same. Another great one is points of inflection for fa jing. I was initially taught to fajing as the first part of lan que wei, and directly after dan bian (at the [b]first[b] part of the circle not the end like shown in 1:03!). Now, my teacher changed how he teaches and tells me not to do that. Another change he made is the number of turns in six sealing four closing. Now we tend to go out directly more along the lines of 'lao jia'.
It is in fact a spectrum, the idea of 'frame' as far as I am concerned is the basic idea which informs the ideas people use to define their frame. Being partial to certain applications is another big one. For example in the entry to lan que wei you demonstrated both hands in front of the face turning into palms. Then circling around. I can show you a variatoin where you turn your body slightly to the right and the right hand shoots out in front versus just closing in a hold the ball style squeeze before peng. The girl does this at 0:31 in the video
https://www.youtube.com/watch?v=_6Am-CKRGak. The point is that depending on your intent of application you can slightly change the form too, but it is the same move.
This is why I like Chen style so much, there is a type of freedom of expression within the form, which comes out of the silk reeling aspect of the form i feel, the circle, inflection points on the circle. Once you understand this everything looks like one form with different expressions. Ex. 0:41 in the above video, which is a somewhat unusual place to fajing. But sometimes pepper and bells like this are thrown in for flavor and excitement. Just my perspective.