I tend to do better by pushing FTP up than pulling it. I'm still seeing huge and consistent gains from peak to peak.
Look at the power levels table (Table 2)
here. Look at the differences between training in zone 3 and zone 4. All of the same adaptations are represented in both zones. More in zone 4, but it's not like zone 3 is abandoning your threshold training. I can train sweet spot in high zone 3 for five days in a row. That's better than a day in zone 4 (for less time) followed by a day in zone 2 to recover, in my opinion.