It's literally impossible to eat a zero-fat, plant-based diet as all plants contain carbs, fat and protein (not by accident, I'm guessing). And nobody is advocating a diet lower-in-fat than is capable of offering sustainable health benefits.
As far as not needing carbs for health? That would depend. One can certainly get by without it for sustained periods, in terms of energy, and the variables with which we can currently measure. But in terms of health, I'd be cautious to make any health claims that weren't backed up by multi-generational data.
In the world of nutrition reductionism, in which the majority of both high and low-carb gurus/doctors operate, these waters are eternally being muddied. The best we can do for people os to be clear that there is much we do not know about nutrition, and therefore to a certain extent each of us who is skirting the borders of extremes (me eschewing all animal products; you getting as close to zero carbs/plants as you can manage) should be made aware that we are taking various gambles.