I'm not sure if it's quite accurate to say that the efficiency cores aren't fully utilized; it looks more like some of these apps are second guessing the OS and going out of their way to avoid using the efficiency cores (probably by only spawning one thread per P core, since macOS doesn't let apps directly control thread affinity).

Most of the time, that is probably the wrong approach for an app to take, but maybe DAWs have latency requirements that can't be met when E cores are in the mix. But that's something the DAW vendors should have to document and justify, because it's just as likely that they're making assumptions about E cores that don't hold up over time across the full range of chips.