because the condition “any single future is ready” is in some sense a “weaker” condition than “all of the futures are ready.”

Ugh, I feel a chunk of my soul get chipped away whenever I hear an argument like this. That’s why, despite all the shortcomings, I’ve been clinging to a particular non-mainstream language for years now. I don’t have much more soul left to grind after 10 years of getting exposed to this in C++, Python, Java etc.