I'm glad you brought this up Punisher73, because I think this line of reasoning is often repeated but full of holes.
First of all, the statement from Hwang's
The History of the Moo Duk Kwan that you specifically quote is yet again another ridiculous white lie. Of course, it no doubt has some truth to it. But have you actually read copies of the books available in 1937, or published before 1937? Many of them are easy to access in digital form through the
Hawaii Seininkai. The biggest way to blow this theory out the water is to notice that none of these books describe the Moo Duk Kwan kata syllabus (or any other style like Shotokan or Shitoryu) with enough photos or illustrations to be able to reconstruct the kata without an instructor. Even today's books have only managed to capture most of the details necessary (but not all!) that you need to perform the kata. (see below for a real example of this)
Secondly, the argument that Hwang read Funaoshi's Karate-Do Kyohan and then based his karate on it can't be true. The techniques and methods illustrated in the book are different.
Take, as an example, Funakoshi's
Karate-do Kyohan published in 1935. It was easily available in 1937. This was the second major book that Funakoshi published, and unlike later editions all the technical photos were of Funakoshi performing the moves himself. The first was ultra rare as the original manuscript that he wrote and the printing plates for it were lost in the 1922 Great Kanto Earthquake, which he mentions in this (1935) edition.
If you consult the
Neptune Publications re-tranlsation, arguably the most word for word and picture for picture accurate translation to English, you can prove this to yourself.
For example, on Page 43, Funakoshi illustrates Heian Shodan. His ready stance is totally different than modern Shotokan and the famous Moodukkwan chunbee. Our chunbee is most similar to the Renbukai style. Toes straight, fists in front of the belt, one fist apart, etc. Funakoshi's has his feet very wide apart, toes pointing out at 45 degrees and fists in front of his thighs. Why then does Hwang not do it this way, if his model is Funakoshi's famous book?
Regarding an example of very few pictures, you can also look to Funakoshi's book. Heian Shodan is very well explained and illustrated with photographs. However, Heian Nidan has almost the same number of moves as shodan, but only 7 photographs. Other problems exist. Bassai Sho is not in the Kyohan at all. Kanku (kong sang koon) has only 8 photographs and is impossible to perform properly with only written words! Seisan has only 4 photos... I think you get the point.
It is possible he "learned" some things from the library at the Yongsan Rail yards, attached to the Imperial Japanese Army military base that he worked at (if it's true that he worked there at all like he claims), but I'm pretty sure he didn't learn Karate from books.
You do realize that the Ministry of Transportation was an arm of the Imperial Japanese Occupational Government in 1937, right? If anything, Hwang had a really good motivation to hide the names and identities of his teachers - or else, why wouldn't he just come out and say who it was? So, to confuse the rest of us, he just said "Oh, I learned it from books I found in the library" and continued his usual vague stories of his shady past.