The previous gentoo init system was already better than sysvinit and initscripts.
I still prefer and use systemd though.
And why wouldn't you compare it with the systems it actually competes against and replaces rather than against something that was barely used any more before systemd even stated development? The comparison with sysvinit, suggesting that those that do not use systemd advocate sysvinit instead, is simply a flagrant straw-man designed to make systemd look good.
I would say that's a meaningless comparison and those other systems were never considered as real replacements. At that time I don't remember OpenRC getting any traction outside of Gentoo, and the distros using Upstart were already unhappy with it. Adding to that, systemd explicitly was targeting distros that used a lot of sysvinit scripts and was intended to be used as an upgrade for them. It's largely succeeded at that.
So the year you're looking for isn't when OpenRC was introduced, but rather when Gentoo started using the OpenRC style of init script, which happened much earlier - it's definitely been like that since I started using Gentoo, at least since 2003 or so.
It's actually a misconception that sysvinit is the whole init system; sysvinit is PID 1. Gentoo still uses sysvinit for PID 1 by default. What matters is what your service manager is - that's OpenRC here.