I originally posted this on SuperUser because I discovered this behaviour on my home computer, but this seems to be a general issue on UEFI systems, thus I'm posting here too; I also hope someone here can shed some light on what's going on.

Italian version of Windows 7 x64 SP1, same installation media used for both situations.

When running on BIOS systems, the boot manager is fully localized, both for the loading screen and for the F8 boot menu. When running on UEFI systems, the boot manager always runs in English, even if it's correctly configured to use the it-IT locale, as BCDEDIT clearly shows:

Windows Boot Manager
--------------------
identificatore          {bootmgr}
device                  partition=\Device\HarddiskVolume1
path                    \EFI\Microsoft\Boot\bootmgfw.efi
description             Windows Boot Manager
locale                  it-IT
inherit                 {globalsettings}
default                 {current}
resumeobject            {9ef36aa6-4188-11e3-909d-d32f0c3871c8}
displayorder            {current}
toolsdisplayorder       {memdiag}
timeout                 30

Caricatore di avvio di Windows
-------------------
identificatore          {current}
device                  partition=C:
path                    \Windows\system32\winload.efi
description             Windows 7
locale                  it-IT
inherit                 {bootloadersettings}
recoverysequence        {9ef36aa8-4188-11e3-909d-d32f0c3871c8}
recoveryenabled         Yes
osdevice                partition=C:
systemroot              \Windows
resumeobject            {9ef36aa6-4188-11e3-909d-d32f0c3871c8}
nx                      OptIn

I also noticed something strange here; the motherboard setup shows "Windows Boot Manager" as the main boot option, while the actual boot disk is listed as the second one. Looks like the Windows Boot Manager is actually being loaded from somewhere else than the first partition of the first disk... what's going on here?

Update

I've also checked the EFI boot manager using bcdedit /enum FIRMWARE. That one looks correctly localized, too:

Boot Manager per firmware
---------------------
identificatore          {fwbootmgr}
displayorder            {bootmgr}
                        {9ef36aa4-4188-11e3-909d-d32f0c3871c8}
                        {a30e8550-47e4-11e3-9ad1-806e6f6e6963}
timeout                 1

Windows Boot Manager
--------------------
identificatore          {bootmgr}
device                  partition=\Device\HarddiskVolume1
path                    \EFI\Microsoft\Boot\bootmgfw.efi
description             Windows Boot Manager
locale                  it-IT
inherit                 {globalsettings}
default                 {current}
resumeobject            {9ef36aa6-4188-11e3-909d-d32f0c3871c8}
displayorder            {current}
toolsdisplayorder       {memdiag}
timeout                 30

Applicazione firmware (101fffff)
-------------------------------
identificatore          {9ef36aa4-4188-11e3-909d-d32f0c3871c8}
description             CD/DVD Drive

Applicazione firmware (101fffff)
-------------------------------
identificatore          {a30e8550-47e4-11e3-9ad1-806e6f6e6963}
description             Hard Drive