SPServices is only a wrapper around the (oldish) Microsoft SOAP services,
So this has nothing to do with SPServices
The SOAP interface:
https://msdn.microsoft.com/en-us/library/websvclists.lists.getversioncollection.ASPX
dictates one strFieldName is required
for alternatives see:
How to get a old version of list item?
Retrieving SharePoint file version properties from the web API
