Thanks! It's a pleasure!

How would an upright stance help him get smarter?

My comment about the squids was just meant to rebut the claim that large organisms will invariably have four limbs. Yes, they'll probably have fewer limbs than a centipede or isopod, because the square-cube ratio makes limbs thicker, but maybe not as few as four. Now that I think about this, though, this only applies to land organisms like the coconut crab, the goliath bird-eating spider, or Pando (who has many more limbs than any centipede!), so the squid wasn't really relevant. A lion's mane jellyfish might be 30 meters in length and have 1200 tentacles, because there's no issue of them buckling under compressive stress; they're floating in the water.

Alex was already bipedal, as it happens, being a bird; I was just saying that evidently hundreds of grams of brain mass aren't necessary to be able to count, use symbols, and draw comparisons between objects. African greys also use tools to scratch the backs of their heads, pass down oral culture from generation to generation, live long enough to remember it for decades, live in large flocks, and drive around in tiny cars with joysticks. If I were somehow revived from suspended animation two million years in the future and humans were extinct but African greys were a spacefaring species, and I had to guess how it happened, I might guess:

1. They became pack hunters, feeding on birds such as pigeons, creating stronger evolutionary pressures to outwit their prey and to coordinate for hunting, as well as to learn to make weapons and traps. This enabled them to increase their nutrient intake.

2. They started living in smaller flocks, perhaps due to the necessity to escape from humans trying to capture them as pets, or perhaps because they adopted a less herbivorous mode of life which couldn't support such high population densities. This enabled their culture to innovate more rapidly.

3. They started making tools rather than just using them. Some stone-age equivalent of Lawn Darts would be totally adequate for hunting non-avian prey, perhaps incrementally developed from a practice of just dropping rocks on its heads; a wattle-and-daub birdhouse with a door would greatly diminish the threat from somewhat larger but dumber nocturnal predators; twine enables snares for smaller prey; nalbinding sweaters might enable the colonization of cooler areas;

4. They grew a little larger, perhaps after the humans went extinct and the forests grew back. Grey parrots don't normally get bigger than 600 g, but female harpy eagles can reach 9 kg, and eat prey in the 2.5-9 kg range, mostly sloths, while remaining entirely capable of flight. Being larger might give the parrots a little more body-weight budget for a brain, though it doesn't seem to have helped the poor eagles that much, but also a little more body-weight budget for clothing (like a hermit crab's shell) and tools. It's totally plausible that some populations of grey parrots might have evolved into formidable 2.5-kg pack apex predators, then started engaging in territorial warfare.

5. Pastoralism and agriculture developed, since once you have a territory you can securely hunt within, you can muster more warrior parrots to defend it if the territory is full of productive, easily edible animals like sheep, allowing you to feed more warriors; and this goes double if you can supplement your meat with lots of calories from things like grains.

6. Fire use developed for warfare purposes before being redirected to other purposes such as cooking and smelting. Fire is incredibly dangerous to birds, not only because of their easily-burned feathers but also because of their delicate respiratory systems; which means that whichever flock can somehow work out a way to drop hotshots on their enemies without dying in the process can become the parrot equivalent of Mongols (or Bantus, Conquistadores, or Indo-Aryans).

Honestly, though, the humans have no idea what is or isn't necessary for the development of intelligence. They've only seen it happen once, and they forgot what that was like.