There are several good reasons for this, rather then repeating them I'm just going to point to the Debian announcement.
This blog post is to let all Fedora users know that starting with Fedora-26 / rawhide as of today, we are making the same change.
Note that the xorg-x11-drv-intel package has already been carrying a Fedora patch to not bind to the GPU on Skylake or newer, even before Debian announced this, this just makes the same change for older Intel GPUs.
For people who are using the now default GNOME3 on Wayland session, nothing changes, since Xwayland always uses glamor for X acceleration, just like the modesetting driver.
If you encounter any issues causes by this change, please file a bug in bugzilla.
The "for all recent Intel GPUs" in the subject of this blog post in practice means that we're making this change for gen4 and newer Intel GPUs.