I can see now why I couldn't find “'This' can also be used as argument for writing all non-static data of an UDT instance.” because you are not using it.
You have added another sentence which is OK, but we are still in the position when I wrote "I read those but, to my mind, requires quite a leap to realize that 'Put #f, , this', for example, is within those definitions."
It is still not obvious from the latest data
paragraph that we can use 'Put #f, , this', for example.
It is not obvious to me – maybe I am being a bit thick.
I think that you are making the cardinal error that many Help authors make by over estimating the expertise of the reader. You are assuming that the reader fully understands 'This'. To my mind, we should always write to the lowest common denominator. Experts won't mind because at one time they belonged to the lowest common denominator.
If 'Put #f, , this' is not specifically referenced, many readers will not get it, especially newcomers.
At the bottom of Get and Put are some examples. It would be worthwhile to have an example showing 'this' being used.
If anyone thinks that I am being over critical with this post, then say so. Equally, if you agree with me, then say so.