Heart Rate Drift test showing high aerobic threshold?

1 month ago I did the heart rate drift test at 155 bpm and I got a 3% drift. This past month I have done only zone 1 & 2 running to develop a base (I kept every run below 155 bpm). I have about 5 years of running on and off experience due to injuries, but I have never done low heart rate training. Today I did the test again with a slightly higher heart rate to get the 3.5%-5% drift that is recommended. I averaged 158 bpm and got a 1.6% drift. The next time I do the test I would aim for 165 bpm, but this seems too high to me. I am a 30 year old and according to the MAF formula my aerobic threshold should be around 150. I know not everyone’s heart rate is the same, but this seems a little too far off and makes me wonder if I am doing this correctly. However, when I was running at 160 bpm today for an hour I could nose-breath and I could also easily carry on a conversation at that pace. 

Some more information: Temperature was the same at about 55F degrees. Similar humidity. I ran on the same route with similar wind conditions. I have a Garmin 965 watch and a Garmin chest strap for monitoring heart rate. My resting heart rate is 50. My max heart rate is around 200 I believe as I hit 195 on a hill climb a few months ago and felt like I had a little more to give.

Just looking to see if anyone else has experienced this or maybe some guidance to explain what I am doing wrong. Thanks in advance!