Home button cable plug in

So, I've been fixing phones for quite some time, but I've noticed a few things when replacing the LCD and home buttons. Some replacement screens have the connector for the home button to plug into and some don't. Ive looked many places and can't seem to see or figure out how it works. What about the parts which do not have the home button cable (not the home button itself but the one that comes seated on the LCD). Some ifixit parts come without it, and some do (even same models in the same shipment).. Is there a way to actually switch it over?

Thanks,

Beth - Experimac