DavidPhillips is right; there is no way that you installed a kernel-source RPM for a different
kernel than the one that was already installed, and the kernel it went with was installed as well.
That's really not the point of having a compiled kernel and the kernel-source available as separate RPMs from each other.
If you install a kernel RPM, it will install a new kernel. If you install a kernel-source RPM, the kernel source will be unpacked to /usr/src and that source folder will be linked to /usr/src/linux. That's all that happens when you install a kernel-source.rpm, because the intention is that you are either going to compile a custom kernel (if it's a new kernel and not the one you already have installed), or compile some outside drivers against the kernel source (if it's the same kernel you're currently running). The same is true of kernel-header RPMs; I've not used them, but they appear to be some kind of "kernel-source lite", which you can use to compile drivers that don't need the full kernel source, but only what in other respects would be called "development headers".
So I think that you're mistaken about your previous experience, but this is not a surprise, as in the early days of Linux use it's not always easy to keep track of what's happening when you don't know what's happening
. Maybe you had the kernel-source for your current kernel installed and did a sytem-wide update which updated both the current kernel and its source. That could possibly happen, using tools like up2date.
Glad the links are helpful.