There are three possible scenarios:
- Both flags are invalid, in which case your first flag shouldn't have been marked as helpful,
- The first flag is valid and the second one is not, in which case they were both handled correctly,
- Both flags are valid, in which case your second flag shouldn't have been declined.
And there is another less obvious scenario, where both your flags are invalid but the moderator who reviewed your first flag though that it had at least some merit, so they decided to mark it as helpful.
None of the questions was migrated, which tells me that the moderator who marked your first flag as helpful didn't agree that the question should be moved to Wordpress Stack Exchange. So I'd say that scenarios (1) and (4) are the more likely ones.
In any case, why does it matter? It's even possible that both flags where handled by the same moderator. There should be consistency in moderation actions, of course, but at the end of the day we are only human. And a single flag is such a minor detail in a moderator's day, especially on the vast wilderness that is Stack Overflow.
Keep on flagging, if you feel your flags have merit, it's just a communication mechanism nothing more.