True, but I'd be happy if Python were to take a step in the formal direction here. I don't think we want to write standards-like documentation, of course, but adopting a bit more precision couldn't hurt and might help.
More precision is good if we can maintain accuracy and say what we actually mean. I've been trying to document things that return true or false as returning true or false rather then 1 or 0, but that's not consistently done yet.
I think it makes sense to adopt the standard definitions of the requirements terms "should", "must", "may", etc., using the definitions from the IETF RFC (deviation would add confusion, though we should feel free to copy the definition text if we can do so without copyright problems).