I took a quick look at Jonathan Cainer's website and my understanding is the same as yours, the chart in generated instantly. Has Cainer anything to do with this process, is the key question here. The answer is probably yes but you need to understand how this works.
There will be a background computer program which will do two key things.
Firstly it will generate the chart itself - the diagram that you will be able to print out. This is the easiest step and there's loads of computer programs that can do this. There are many on the internet that will do this for free and be just as accurate.
Secondly the program will identify
a) planets in signs
b) planets in houses
c) planets in aspect
d) optionally any other points or bodies regarded as important by the author - such as the Nodes of the Moon, Chiron, Various asteroids and aspect patterns.
For eaach of these identified characteristics the program will pull from store a paragraph and add this to the final 'Report', at the end of this process the document will be emailed to you and you can print it out.
If we have any members who work for lawyers or are lawyers they will recognise the process of using stock paragraphs to create a contract.
Now I would hope that these paragraphs have indeed been written by Cainer (though there's no guarantee) and clearly the computer is not able to synthesise the material to create a considered evaluation. That is you will get more by going to see Cainer and getting him to do a private reading. It will however cost you an awful lot more.
Every single website and every single computer program that offers 'Reports' works in the same way. Some may be a bit better on some synthesis, some may be better on the underlying Astrology, some even let you write your own paragraphs (and I suspect this is what Cainer has done) but ALL of them are inadequate compared to consulting a living Astrologer and getting him or her to give you a private reading.
Are they of any value at all? Well I'd take one by Liz Greene, or Cainer, or other top Astrologer rather than someone I've never heard of, all things being equal but to be honest I wouldn't pay money for any.