What are the catch characteristic of the Moltres at the end of a Field Research?

I will be completing my third Field Research this evening and be rewarded with a Moltres encounter. The first time, I used a Golden Berry and an Ultra Ball and hit and caught the Moltres first throw. So I thought maybe the Moltres was auto-catch, if hit. The second time, I used a Pinap Berry and a regular red ball and hit the Moltres first throw, but did not capture it. So I knew that the Moltres is not auto-catch, if hit. I proceeded to pepper it, maybe 15 times, with Pinap Berries and Ultra Balls, most always hitting it with curve balls, with a fair frequency of great throws, and eventually capturing it. So now my hypothesis is Moltres has a very low flee rate, maybe zero, with the conclusion that I should use Pinap Berries and Ultra Balls as long as needed to capture it. What is your experience and advice?