The files offered on this download page are for manual install with fastboot, they are not OTA update files for FP6. You can’t install those via recovery like you can with the real OTA update files I pointed to.
In the past there has been no visible overall direct relationship between the two different availabilities.
I would happily accept if there is now somehow, but I’m waiting for founded confirmation.
Fun fact: If you alter the download links and delete the “IMG-” from it, you will get the OTA update files instead of the manual install files from the download server you linked to, too. It also perfectly delivers the new 4.1.1 OTA update file if you want, it just doesn’t list it. (Want to see? … I just changed the address from “ota” to “images”.)
Even more fun fact: the 4.1.1 update file for manual install is available, too, if you know the direct link. (Want to see? … I just added the “IMG-” back to it.)
The download page just doesn’t list it yet.