now if you see "config in yaml" you know nothing, zero, nada, about the format because all versions are so different and everyone implemented the version at the time and didn't bother to mention version. not to mention you can use a dozen syntaxes for yaml/toml and each application may not understand them all.
all this is so silly. we will stick with json and informal-ini forever one way or another.
Many commonly-used standards today weren't created by a bunch of wise men in a room thinking how to bestow their wisdom upon the rest of us, they often originated in real-world applications, were refined over a period of time based pn real-world experience, and then became a standard.
TOML is the same. I hope it will become an RFC some day. We just need to fix a few outstanding issues first.
Most commonly used TOML parsers support 1.0; adding 1.1 support should be pretty easy as the changes aren't that large (I did it in the parser I maintain, and it's 10 lines of code or so that had to be changed, most of them quite trivial).
Without that your config file is a boobytrap, with it everything is fine and your parsing libraries can even be backwards compatible.
(and mentioning version could be a requirement in a future version)