The whole point of training is to stress the body. By wearing super shoes you do not receive an equivalent stimulus unless pace/intensity is adjusted, and when intensity is increased, you receive the same stress to the body as in regular trainers.
But "the body" is not just one thing that is stressed in one way. Take this for what little it's worth (I know next to nothing about the subject), but if the super shoes reduce the stress on your legs, then the faster running they allow may put the same stress on your legs and more on your lungs, allowing more improvement. Or the faster recovery they allow me let you stress your lungs more often. I'm sure it's a lot more complicated than just legs vs. lungs, but you get the idea.
It’s the one thing time the people against the 4% fail to understand because they don’t want to understand. You can either ran the same effort in a shoe that provides a better economy, aka faster or less effort to run the same time/pace less efficient shoe otherwise the impact is the same.
The difference here that you could train in fast shoes, typically lightweight, which were really racing flats that beat you up more or train in, typically heavier, cushioned shoes which were slower that left you more fresh. Couple that with changes in training methods, despite 80/20 easy/hard there is still a lot of time at threshold for elite at 100+ miles per week.
Now we have foams which are both lightweight (fast) and cushioned (less impact) our performance improves in both training and races. This is no difference comparatively to training in racing flat on a track but instead we can do it on the road.
Some “older” runners complain really should of run in different shoes and they would have been faster. Others complain because they did not have this “technology” and others still become of a lack of understanding on the subject and economy improvement, read 4% = run 4% faster, great marketing but almost forgot that the streak is 5% more efficient than the Pegasus anyway.