Thank you Sinhaa,
You saved me hours of process-of-elimination tests to narrow this down. Yes, it turns out the "Filter Storage Virtual Machine by Cluster" is a component of the SLO Pack which is installed on my source WFA system and not the destination WFA system. I noticed that several other filters with the same "last modied dates" referenced SLO concepts which is how I associated it with SLO pack.
I happened to use a Filter from SLO in a Finder I created and had NOT realized or noticed it was was from SLO and not a cDOT-builtin filter.
BTW, once I knew what the culprit Filter was, the way I determined what (in my code) was USING IT was to attempt to delete the filter. It is a messy way to determine it, but I've found that in WFA, attempting to delete something which you know is in use, but you're NOT sure by what, is to try and delete it. After it asks if you are sure you want to delete it (say yes), it will fail and show you what other component is using it. Wonder if there is a more straight forward way to see those dependencies.
This may be my only problem but if not, at least you gave me some tools to interpret and research any other such mishaps. I had not considered the "un-export'able" filters/etc issue.
Thanks again.