Any distribution that doesn't ship modifications to the kernel immediately "adopts" the latest kernel on release, whatever that means. For example, Exherbo had it immediately since users are directed to download their kernel sources from kernel.org; ignoring that, the package for the kernel headers (for building e.g. libc) also were updated nearly immediately, from the main git repo:
commit 629e1b2b1d30608e3b3af74de0c7a220009bba54
Author: Timo Gurr <tgurr@exherbo.org>
Date: Mon Jun 22 18:49:20 2015 +0200
linux-headers: version bump to 4.1
I'm also not sure how you can claim a linux distro is the first without exhaustively checking all others. As you can see, it is highly probable Solus was not the first.
commit 629e1b2b1d30608e3b3af74de0c7a220009bba54
Author: Timo Gurr <tgurr@exherbo.org>
Date: Mon Jun 22 18:49:20 2015 +0200
I'm also not sure how you can claim a linux distro is the first without exhaustively checking all others. As you can see, it is highly probable Solus was not the first.