Comment 5 for bug 1975860

It's expected behavior for MD_LEVEL not to be set for inactive raid devices. Looking at 64-md-raid.rules,

# do not edit this file, it will be overwritten on update

SUBSYSTEM!="block", GOTO="md_end"

# handle md arrays
ACTION!="add|change", GOTO="md_end"
KERNEL!="md*", GOTO="md_end"

# partitions have no md/{array_state,metadata_version}, but should not
# for that reason be ignored.
ENV{DEVTYPE}=="partition", GOTO="md_ignore_state"

# container devices have a metadata version of e.g. 'external:ddf' and
# never leave state 'inactive'
ATTR{md/metadata_version}=="external:[A-Za-z]*", ATTR{md/array_state}=="inactive", GOTO="md_ignore_state" <==
TEST!="md/array_state", ENV{SYSTEMD_READY}="0", GOTO="md_end"
ATTR{md/array_state}=="|clear|inactive", ENV{SYSTEMD_READY}="0", GOTO="md_end"
LABEL="md_ignore_state"

IMPORT{program}="/sbin/mdadm --detail --export $devnode"
ENV{DEVTYPE}=="disk", ENV{MD_NAME}=="?*", SYMLINK+="disk/by-id/md-name-$env{MD_NAME}", OPTIONS+="string_escape=replace"
<SNIP>

LABEL="md_end"

So IMPORT{program}="/sbin/mdadm --detail --export $devnode" is skipped if the array is inactive.