>Are you sure?<
Yup
>Is this normal for some guys?<
Its normal for everyone.
> I thought the glans always swells with the rest of the penis??<
They do but they don’t contain erectile tissue like the CC/CS.
>When I have a rock hard erection, my glans is rock hard too.<
Either for you rock hard is what others would consider soft or you’re just misunderstanding the anatomy and assuming that the CC/CS you feel through the glans are part of the glans.
http://www.bart … om/107/262.html
http://www.bart … /illus1154.html
If you need more detail than that you’ll need to ask one of the anatomy experts here.