IOW, he is saying that "stand your ground" is limited to the phrase "and has no duty to retreat." The remaining statutory language is sufficient to find immunity, in this case. Either way, Zimmerman's case presents the exercise of lawful force in self-defense.
Said another way, even if the law DID include a duty to retreat, Zimmerman would prevail. Keep in mind that "duty to retreat" doesn't attach at every moment. It exists only when confronted with force. If the confrontation with force renders a person unable to retreat, the law will not hold them to a duty to retreat. The law will not require a person to do what the person cannot do. The clock starts with the first blow, not with Zimmerman getting out of his truck.
But the prosecution will argue that he instigated it by following him and even after the initial punch he could have retreated at any time until the last 40 seconds of the "fight" when Martin was on top of him. So he was able to retreat until the last 40 seconds.
Since you know that this argument is coming, then why not avail your client of both from start to finish -- the full statute. He had no duty to retreat at the time the assault began and no ability to retreat as the assault played out.
Use both arguments -- not one or the other. Why distinguish one from the other and then go with the harder standard to meet???