That's what I presumed - optimising for speed rather than simplicity. That does sound like I meant it negatively but I think it's a good choice here with a choice that happens every single draw call. It's trivial to make a copy if one needs it anyway; it's just a new habit to get into (since I almost always do make that copy).
I only noticed it when it refused to compile and wanted to know if it was a decision that's been made for SFML3 or it's being tried out so I think you've answered that now, so thank you.