The first interval session of the marathon block was successful: 6.8 km in 42 minutes, dynamic effort, and a strong finish with good sensations.
The workout did become a little hotter than pure threshold in the second half. The third and fourth 4-minute reps moved closer to 10K effort, with heart rate rising into the low 180s.
That is not a problem for one session, especially because you finished whole and motivated. The key carry-forward is to keep early quality controlled so the plan builds fitness without spending too much mental or physical energy too soon.
Takeaway. Quality is landing well, but do not race the workouts. Keep the first half of interval and fartlek sessions controlled, then only progress if the effort still feels smooth.
Next step. W01D6 Fartlek Run. Controlled aerobic fartlek to add rhythm without turning the week into back-to-back hard efforts. Keep the fast parts smooth, not all-out.