What I read is that you power was delayed by 1-3 seconds - and the key thing now is that ‘analyzing’ segments can’t be done by simply reviewing the TR interval segments.
My opinion - for 30/30s the Kickr v5’s standard mode is a better choice than erg. Because its more like doing the workout outside, and learning to use cadence/power to cover small gaps that open up (or short changes in gradient).
However Erg can be perfectly fine, it just requires some practice to quickly ‘dump’ extra power at the start and then back off and keep cadence the same. More of a special skill for erg.
When it comes to adaptations in your legs, prescribed power is an interesting topic and I wrote something about it here:
and be sure to read the linked article about some of the research and potential adaptations. From that TrainingPeaks blog post, the basic idea is that the higher target power of 30/30s (versus 3-min or 4-min classic vo2 intervals) can result in greater adaptations in leg muscles.