I get these can be unstructured but ... they can be structured.
it's my understanding these are very good for runners to get better control of managing a consistent race pace - ie it's common for runners to train for months/years and still get hit by race adrenaline, going harder than training, etc and have fairly varied race pace vs their training runs.
Any idea why garmin doesn't include them or a version of a run where your recovery is your base pace?