Gone in 10 seconds...
...my good impressions of El Reg as a tech-savvy pub.
This attack does *not* give you anything you could not get by using a USB boot, CD boot, or PXE (network) boot.
The only situation where you *do* get more than that is in "kiosk" type situations (where the CPU/case/disks are locked away but the keyboard/mouse/monitor are accessible).
And even then, the statement "With access to the shell, an attacker could then decrypt Linux machines" is totally wrong.