Improved named arguments

Twig doesn't care about PHP functions. Twig only cares about its functions, and here, I don't see which problems it solves. If some default values are wrong, we can just fix them. So, it looks like it fixes a problem that does not exist.

Except perhaps if someone maps a PHP function that has some of the problems you mention directly as a Twig function and it uses the function with named argument, in which case (it never happened) we would recommend the user to fix the mapping.