I have not really understood what is meant with "as there is only one list counter per list level". Playing around with this attribute and wondering why it does not work on lists with level > 1 in LO I came across this:
https://lists.oasis-open.org/archives/office/201203/msg00014.html

So seems it should be only supported for lists of level 1. Do you happen to know a better reference than the email thread I linked here?

In any case please improve this comment to make more clear why only listLevel1 is cared for.