I had never noticed xxd has no header until comparing its output against dbgblock.py. Turns out these headers aren't really all that useful, and even sometimes wrong in dbglfs.py.
This script is basically the same as xxd, but with the other debug script's block address format: $ ./scripts/dbgblock.py disk -B4096 1 block 0x1, size 20 off data 00000000: 00 00 00 00 00 03 00 08 6c 69 74 74 6c 65 66 73 ........littlefs 00000010: 40 03 00 0c 80 04 00 02 02 00 d0 03 00 16 c0 04 @............... ...