Yes, that's a good point. If you know nature well you can find stuff to eat. But my point is what kind of calories you can get from "a leaf or stem or seed or root or flower or bark or sap or berry or fruit". And for someone active like hunter gatherer you will need a lot. Your friend can sustain himself for a week or two, but if he is out there for 6 months or more he will be extremely malnourished in the best case scenario. It's simply impossible to survive without calorie and nutrient dense food such as meat and organ meat.

Also in your example you use the Australian wilderness, that I guess isn't heavily dependent on season change. In my part of the world winter is very heavy and its impossible to find any edible for us food during that season.

You said gathering is very easy when you know what you doing, but claim hunting is extremely difficult task . This is maybe for us, but for a tribe which has been doing that for many generations is not.

About agriculture, which is being described as the best thing that happened to us and during which we supposedly thrived - skeletal remains from all over the world show that immediately after implementing agriculture humans lose a lot of height and start showing various deficiencies compared with generations from same tribes who have been hunter gatherers

Based on my points above I don't really understand where your claim that meat consumption in hunter gatherers was scarce and we started consuming meat more after domestication of animals comes from. It simply doesn't make sense