The problem is: like regexes, there's no 1 true cpio but rather many flavors.

pax's cpio supports[0]:

- bcpio - Old binary cpio format. Selected by −6.

- cpio - Old octal character cpio format. Selected by −c.

- sv4cpio - SVR4 hex cpio format.

- sv4crc - SVR4 hex cpio format with checksums. This is the default format for creating new archives.

GNU cpio supports[1]:

- binary

- old ASCII [hex?]

- new ASCII

- crc

- HPUX binary

- HPUX old ASCII

0. http://www.mirbsd.org/MirOS/cats/mir/cpio/cpio-20200904.pdf

1. https://www.gnu.org/software/cpio/manual/cpio.html