When will the FreeBSD (u)EFI work?

On an experiment of the FreeBSD EFI implementation. I installed
a copy of releng/12 from install media. Which left me with:
# gpart show ada0
=>       40  312581728  ada0  GPT  (149G)
         40     409600     1  efi  (200M)
     409640   31047680     2  freebsd-ufs  (15G)
   31457320    7680000     3  freebsd-swap  (3.7G)
   74788904  237792864        - free -  (141G)

On this Intel based system, I can stab the F12 key to pick
my UEFI bootable OS, or let it boot according to the order
I setup in the BIOS. So far, so good.
I needed a copy of releng/13 to also work with. Installed a copy
from install media. Which left me with:
# gpart show ada0
=>       40  312581728  ada0  GPT  (149G)
         40     409600     1  efi  (200M)
     409640   31047680     2  freebsd-ufs  (15G)
   31457320    7680000     3  freebsd-swap  (3.7G)
   39137320     532480     4  efi  (260M)
   39669800   35119104     5  freebsd-ufs  (17G)
   74788904  237792864        - free -  (113G)
I *assumed* that the install would activate the new install, and I
would boot straight into it. But no. I am still on the previous
install, and worse, I can't get into the new install -- even if
picking it via stabbing the F12 key. I *still* end up in the previous
install. So looking at what might be causing it. I found the following:
# releng/12
# mount -t msdosfs /dev/ada0p1 /mnt/

# ls /mnt/efi/boot/
BOOTx64.efi
startup.nsh

# cat /mnt/efi/boot/startup.nsh
BOOTx64.efi

# umount /mnt/

releng/13
# mount -t msdosfs /dev/ada0p4 /mnt/

# ls /mnt/EFI/freebsd/
loader.efi

Why the difference? When will FreeBSD (u)EFI work as expected?

Thanks in advance for any insights!

--Chris