Following this discussion I took a note to pay attention for traffic alerts at the same altitude. Today my PF alerted me of another plane flying at the same altitude as mine showing 0 altitude difference for at least 10 seconds while the aircraft was at the same altitude. So I suspect the suppression is indeed also based on power level. BTW, I few with Zaon since they first came out nearly 10 years ago. It was never as reliable and accurate as my PF is nowadays.

Ramy