I think part of the problem is the use of the initrd.img and uImage.img in this manner. Those are password-protected zip files with contain the files your looking for, not the actual boot files.
I'm working on writing a proper guide for this process as it's somewhat confusing. In the meantime, to get the firmware to install on your device:
1. Get the boot files:
Download the firmware for your device, unzip it and find the *.img files containing the firmware
unzip initrd.buffalo, it contains initrd.buffalo
unzip uImage.buffalo, in this case it contains uImage-88f5182.buffalo. rename this to uImage.buffalo
the passwords are listed at
https://vanducuy.wordpress.com/2010/08/09/buffalo-linkstation-revived/2. Prepare the hard drive
create a partition table, mbr seems to work for all devices most newer ones also accept gpt
create partition1
format partition1 ext3
mount it and copy initrd.buffalo and uImage.buffalo to it
3. connect the drive to the device and boot it up, after a few minutes it should be in em mode.
4. Prepare LSupdater
edit LSpdater.ini and set no format = 0 and enable debug mode per:
https://herzig-net.de/?page=unbrick_ls-wxl5. Run LSupdater
It should find the device in EM mode.
go to the debug menu and check the boxes as described in (I typically just check them all if starting with a blank drive) :
https://herzig-net.de/?page=unbrick_ls-wxl6. With any luck the firmware install will succeed and the device will boot up after about 10 minutes.
Like I said, I'm in the process of writing up a more detailed guide for this process but I think this should get you going. Let me know if it helps.