Thanks for the clarification.
About 10 minutes into the test is when your HR stabilizes around 167, so I just looked at the remaining 50 minutes and average heart rate for the two 25 minute periods. You do get a low HR drift but the HR dropouts and HR downward trend towards the end make it difficult to calculate the true drift.
Given your Z1/Z2 volume since August, your AeT has definitely improved and but not sure I would set it to 170+.
I will reach out to Scott Semple and request to provide some feedback on your AeT test.
Regarding HR dropout issue, DC Rainmaker has some good articles on this issue. You might have already tried the recommendations to fix the issue, but just something to consider.