The problem is you are using a recovery based on A10 sources to try to decrypt a A11 rom (note the 10 at the end of the filename)
I'm using the April 20 build of pitchblack recovery by dungphp Link and have no issues decrypting
I've tried flashing the recovery that you give me, but it still didn't work (no password asked, I go directly to the main menu).
BUT, it worked if I only push it through "fastboot boot recovery.img", as the current TWRP recovery available on this thread.
I still don't understand why if i flash my recovery, the password isn't asked, but if I push the recovery temporally, is it asked.