https://bugzilla.redhat.com/show_bug.cgi?id=1691999 (filed against rubygem-fog)
https://bugzilla.redhat.com/show_bug.cgi?id=1692129 (filed against ruby, the source package for rubygem-irb)
I filed the second bug. I'd mark it as a dupe, but am not sure about the package.
I don't know what you're talking about (or to be more precise, I understand that kernel-tools is built separately from the main kernel package, and why, but don't see what that has to do with this). There IS a kernel-tools-4.18.15-200.fc28 update included (look under the Builds tab). The current stable version is kernel-tools-4.18.13-200.