That matches my experience.
When I cloned the old HD to the SSD, it "just worked", with no need to contact MS.
When I replaced the old PC with this one, I used the same DVD to install and had to phone MS. I said "old PC replaced, scrapped" and they did the codes thing with no further ado.
The old one was used as a Linux try-out for a while, but that got boring. It went for scrap (minus the hard drive, which I buried with full military honours).