At one time it was thought that software that could beat a human at chess would be, in your lingo, "a shade of AGI." And for the same reason you're listing your milestones - because it sounded extremely difficult and complex. Of course now we realize that was quite silly. You can develop software that can crush even the strongest humans through relatively simple algorithmic processes.
And I think this is the trap we need to avoid falling into. Complexity and intelligence are not inherently linked in any way. Primitive humans did not solve complex problems, yet obviously were highly intelligent. And so, to me, the great milestones are not some complex problem or another, but instead achieving success in things that have no clear path towards them. For instance, many (if not most) primitive tribes today don't even have the concept of numbers. Instead they rely on, if anything, broad concepts like a few, a lot, and more than a lot.
Think about what an unprecedented and giant leap is to go from that to actually quantifying things and imagining relationships and operations. If somebody did try to do this, he would initially just look like a fool. Yes here is one rock, and here is another. Yes you have "two" now. So what? That's a leap that has no clear guidance or path towards it. All of the problems that mathematics solve don't even exist until you discover it! So you're left with something that is not just a recombination or stair step from where you currently are, but something entirely outside what you know. That we are not only capable of such achievements, but repeatedly achieve such is, to me, perhaps the purest benchmark for general intelligence.
So if we were actually interested in pursuing AGI, it would seem that such achievements would also be dramatically easier (and cheaper) to test for. Because you need not train on petabytes of data, because the quantifiable knowledge of these peoples is nowhere even remotely close to that. And the goal is to create systems that get from that extremely limited domain of input, to what comes next, without expressly being directed to do so.