The quota you refer to is more complicated because protein isn't one thing. It's framed as such, but it isn't. There are a vast number of different proteins and they're not at all interchangeable. At an extreme, it's possible to eat as much as 5 times your daily quota of protein and still be deficient in protein. Your body doesn't directly use the proteins you eat - it recycles them into the amino acids they're made from and uses those amino acids to make the proteins it needs. So the protein quota you refer to is actually a number of different amino acid quotas. Your body can make some of the amino acids itself from other stuff, but not all of them. It's essential to get some of the amino acids from food and drink. The use of a single protein quota as a simplification works well enough with animal proteins as they use amino acids in about the same proportions as humans need, but it doesn't work very well with plant proteins because they don't.
I'm not saying it's impossible to get enough of all the amino acids solely from plants. It is possible. But it requires more knowledge and more care over diet. The "it's all protein" simplification doesn't work well enough with plants. You need to get proteins from different plants in the relevant proportions, which works because different plants can have different amino acid profiles.
Some nuts are a great basis for it, though. You can quite reasonably get enough of all but a couple of essential amino acids from a few different nuts alone (and cashews are amongst the best, so you're on a winner there since you obvously like them).
What the frig! That's the first intelligent post I've seen - are you sure you don't want to spout some unsubstantiated heresay or 1970s observation study?? P
On a serious note - well done, as I've said many times, if we can move past the ideological numbskulling, there are some interesting questions about how far we can replicate our natural diets; which your post starts to explore.
I do suspect it may be drowned out in due course but almost worth a separate topic - ie veganism for those post-GCSE biology...
One of the big areas at the moment in biology is breaking apart of the 'monoliths' we previously assumed - ie a calorie from one source doesn't equal a calorie from another, cholesterol is far more different than we understood, same for fats (even sub groups like saturated fats are provably not a group) and likewise proteins as you correctly describe.
Nuts appear to be the closest to meat protein that you can find and so are key for any attempt for a meatfree diet - they do still lack some elements for long range diet, but a pretty good substitute in the short/medium.
This fundamental need for meat (as well as the inefficacy of vegan diets) is what flipped the guidance towards 'meat reduction' Vs meat free diets.
One interesting question is how little meat we might need if we hypothetically wanted to maximise health and minimise impact - some studies suggest it might be pretty minimal to provide all the truly unique nutrients that our bodies require (eg one steak a year sort of volume)
