A perfect use of a past participle without the auxiliary verb "have"
Let's look at a similar pair:
Now gorged on my blood, the mosquito stopped buzzing around my ear and settled on the wall.
This means now stuffed, the mosquito etc.
Having just gorged on my blood, the mosquito buzzed more excitedly around my ear.
This means that the mosquito just finished biting me (perhaps more than once), and now is buzzing more excitedly.
Do you see? The meaning is slightly different. Or maybe I should say the point of view.