Well, not quite, because those features were "accepted" and public and well known and available in basically final form to implement for many years.
So it's not like the standard came out and everyone was like "whoa, new stuff we have to do". It came out piece by piece, and at some point was declared done.
Like HTML5, only more organized and it got finished :)
This is why, for example, GCC and clang have had mature implementations in them for years.
In fact, GCC/Clang/et al having implementations was pretty much a pre-req to finishing the standard because they were used to discover bugs and issues in the proposed standard.
(edit: I'm simplifying a bit, since GCC, et al have had to make bug fixes for draft vs final incompatibilities and bugs that were discovered, but they are still relatively mature)
So it's not like the standard came out and everyone was like "whoa, new stuff we have to do". It came out piece by piece, and at some point was declared done. Like HTML5, only more organized and it got finished :)
This is why, for example, GCC and clang have had mature implementations in them for years.
In fact, GCC/Clang/et al having implementations was pretty much a pre-req to finishing the standard because they were used to discover bugs and issues in the proposed standard.
(edit: I'm simplifying a bit, since GCC, et al have had to make bug fixes for draft vs final incompatibilities and bugs that were discovered, but they are still relatively mature)