import/export and topic_id

[EightBitz]

If I programmatically add content to an export file, I have to give each topic a topic_id. I'd like to know if I'm properly understanding how this works.

What I've seen so far is:
Within a given export file, each topic_id should have a value of "Topic_<nn>" for example:
topic_id="Topic_1"
topic_id="Topic_2"
topic_id="Topic_3"
(etc ...)

As a test, I created 3 new Pathfinder realms, and populated each with one spell.
Let's call them Realm1, Realm2, and Realm3.

After adding one spell to each, I did a full export of Realm1 and a full export of Realm2. Then I opened the XML for each file to check the topic_id of the spell I added to each. Each spell in each realm had the same topic_id value: topic_id="Topic_2"

I then imported Realm1 and Realm2 into Realm3, and did an export of Realm3. The result was that I had Realm3 with 3 spells, and the export showed three different topic_id values.
topic_id="Topic_2"
topic_id="Topic_3"
topic_id="Topic_4"

All this tells me that while the topic_id value should be unique within any given export file, it does NOT have to be unique relative to existing topics in the Realm you're importing into. That, apparently, will sort itself out during the import process.

So, if I create three export files, and each one has two to three thousand topics, I don't have to make sure that the topic_id values are unique across all files, just unique within each file.

Is this an accurate assessment?