The definition "overlap" isn't meant in the context of multiple SVM;s. You can have as many SVM's and LIF's on the same subnet. it also not there to address security in any way - it's just a technical mechanism. You can see that by default the NetApp own MGMT ports all configured on the default ipspace.
The idea of IPSpace is that if you are a service provider, and want to set the same IP for all the customers SVM's -as a "standardization" Then you can use this feature.
See here - https://docs.netapp.com/ontap-9/index.jsp?topic=%2Fcom.netapp.doc.dot-cm-nmg%2FGUID-40654629-C4E6-41A9-8614-D2A019E57909.html
- Most customers don't need this feature at all - even not the ones with overlapping subnets as s long as they access their own dedicated SVM with its own default gateway (the article a bit misleading when it talks about static routes)
One more thing about ipacpaces. if for some reason you do choose to use it - it will require you to assign a dedicated set of ports/vlan to that ipspace.
I do encourage to:
* Put this interface on dedicated MGMT subnet.
* Secure the IP (and the other MGMT IP's) with external firewall/access-list to prevent users to access them.
* Put NetApp firewall rules on it as well, so a hacker or malware compromising one device on that MGMT subnet - cannot hop to these ports as well.