Quote Originally Posted by zedeeyen View Post

No it doesn't. Боб Уайтман's table only explains the orthography of soft and hard vowels and how they relate to preceding consonants. It doesn't explain the actual distinction between soft and hard consonants at all. To learn that you have to hear it, and to be able to hear it you need an understanding of the basics.
But even that simple thing is not explained in textbooks, it does not take neither much place nor much time, but gives a possibility for a learner to understand what is what in the written form. That's like understanding how to pronounce ce, ca, que, za in Spanish.
You asked why beginner texts tend to ignore the subtleties of soft and hard sounds
These are not subtleties, but very basic things. Descriptions help much especially with consonants. Something correct still can be written in a textbook. At least you will know what you pronounce wrong. For example a Russian learner of English might not hear or reproduce the difference between w and v, but at least he is told by the transcription that they are two different sounds. A learner who pronounces lya instaed of ля might not even think he makes something wrong.