orchestrator-client uses the sed in the default path. BSD sed does not include flags like -E, -r, --regexp-extended, which results in orchestrator-client --help returning this:

sed: illegal option -- r
usage: sed script [-Ealn] [-i extension] [file ...]
       sed [-Ealn] [-i extension] [-e script] ... [-f script_file] ... [file ...]

Though it could be rewritten to support BSD sed, it's probably safe to assume that the system has gsed installed (as the script already makes the assumption that jq is installed).