Looks great to me.
The Tony Tables should also show the code/"workaround" that does work today. Your proposal isn't letting me express anything that isn't already expressible, right? You're just proposing a new shorter syntax for what's already expressible? So you should show (on the left side of the Tony Table) a valid way to express it in C++20.
Not just "today it's a syntax error, tomorrow it's not a syntax error." That's not a Tony Table.
That's absolutely a Tony Table. He's showing something that you might think would work but doesn't... and now works and does the expecting thing. Sure, he could also show the workaround you have to write today, but not having that does not make this not a Tony Table.
On that note, the paper proposes a feature-test macro. What's the motivation for a feature-test macro? Like, I'm not going to write:
#ifdef __cpp_cool_new_thing
fill(v, point{3, 4});
#else
fill(v, {3, 4});
#endif
If I have to support both compiler versions, I would just write the first thing. Is there a reason to need the macro here?
Barry