Context is noticeably awkward when you get it wrong, and I'd say the article appears to have identified this as a problem and presents it as "this is a problem therefore it must be fixed". But, most of the time, there is not that awkwardness: context is extremely helpful to learners - of any subject.
It also appears that you are describing how to learn to read in an alphabetic system - so it's not immediately obvious that what you have said could apply to "most people in the world".
> But Rodney said: "My dog likes to lick his bone."
The context makes perfect sense and matches the picture. The issue is 'Rodney' didn't actually read half the words.
As an adult, I probably only read about half the words in a useful e-mail. (hopefully with more skill than a child reading a picture book). I wouldn't call that an issue.
I think kids should be rather discouraged than encouraged to rely on context.