My opinion - "Storage System" is a whole unit (Cluster), so the technical case answer is correct. I think that kb is suggesting - By multipath, it means that you can have max '2' paths to the single tape-library(drive). If you have multiple tape-library(drive), then you can connect the other Nodes to those. Also, I think multiple paths does not mean multi-streams from one backup-object, it is only available as a secondary path, in case the backup fails on the current path.
This is also indicated in the following doc:
https://docs.netapp.com/us-en/ontap/tape-backup/configure-multipath-access-concept.html
Ex-
NetApp:
Cluster = STSW-3070-2_cluster
Node = STSW-3070-2_cluster-01
Initiator = 0b [1st path]
Initiator = 0d [2nd path]
Target = IBM 3573-TL_1