The present perfect is particularly used when (1) There is no phrase refering to a past time for the verb. and (2) A "connection" to the present exists.
What the connection is can vary.
"She's broken her leg" would, in the absence of any other connection, suggest that the connection to the present is that "Her leg is currently broken".
But that is not the only possibility, and context can change the interpretation:
Like many other extreme mountain bikers, she's broken her leg, her pelvis, and her collarbone. But now she is back to full health and competing at international level.
The point his that that the "result" of breaking a leg might be "Now the leg is broken" or it might be "Now I have experience of trauma" or it might be "Now I understand what it is like to enter the medical system." These are all "results". So you can't deduce from "I've broken my leg" that the present "result" is "my leg is broken". It could be one of the other results.
McCoard is making the point that even "he has died" might have different results in the present from "he is dead". The choice of the verb "die" is to drive home his message: Even for the verb die the there may be different present results of the event.
What is the "connection to the present" - In this case, it is the description of her as a tough person who has overcome numerous difficulties, such as broken bones. We are describing her now, and that is the connection to the present.
Sometimes the connection is that the event happened recently. Sometimes the connection is that the state continued from a point in the past to the present. In many cases you can rephrase with the past tense, with minimal difference in meaning. Note that British English will use present perfect for many expressions that American English uses the past tense.
So... McCoard shows that there exist contexts in which "He has died" does not mean "He is dead". Sure, the point of this exercise is to demonstrate that this is the case even with verbs like "die". However it is a "dangerous exercise" since in nearly all contexts in which one would say "He has died" then "He is dead" is also true.
H&P say the same. The likely implication of "She has broken her leg" is that "Her leg is broken", but as above, only a likely implication, not certain.
Hewlings gives another sense of present perfect. It may also be used for something recent.
There is no contradiction here. Hewlings does not say the exact opposite, he just gives another example.