I'm afraid I don't have an answer for this, but I will add another related question / problem to this thread:
I have the reverse situation, where the analytics reports participation with tasks where no submission has been received. The tasks are graded quiz / survey / discussion type activities. I'm wondering if the student is entering things in their view without hitting [submit] and this is sufficient for it to register with analytics?
It would explain why in the past I have seen multiple participation numbers for single tasks with only one submission.
If anyone knows, I'd be grateful for some clarity around this.