No, not really - I have no particular opinion about what POSIX chooses to support or not.

But I'm going to go back to my original point. What I do have an opinion about is how reasonable it is for tools not to support a character that is valid in file names, when that character is straightforward to support with everyday, well known syntax.

And when that character is ' ', the standard English word separator, as straightforwardly supported by approximately ever kind of quoting or escaping syntax ever, my opinion about a lack of support is: it's crap.