I assume your testing protocol followed the suggested UA guidelines (15+ min warm-up, gradual increase in intensity, 3+ min stages, fixed incline to speed or vice versa, etc)?
Some thoughts, but I’m no expert.
Pace is a better measure for intensity (and more performance relevant) than HR. Your aerobic and anaerobic capacity clearly improved in speed. I have no explanation as to why your HRs decreased.
Is a 5 bpm difference even significant? Could other factors like hydration, stress or body temperature account for this? If it is significant and HR is representative of intensity, I’d expect AeT to increase and AnT decrease if only aerobic work was done. Conversely, I’d expect AeT to decrease and AnT increase if more anaerobic work was done. Here we see a decline in both HRs, but an increase in speed. Interestingly, AeT/AnT ratios are similar. I don’t know, given 2 samples 2 years apart.
Regular testing (every 6 weeks to several months) would be more informative to determine training effectiveness. If not in a lab, then at least AeT drift or lactate tests, and AnT field tests.