I think the refer to the concept of regular black holes. It is a concept where the BH has two horizons, and within the inner one the metric is no more Schwarzsc

I think the refer to the concept of regular black holes. It is a concept where the BH has two horizons, and within the inner one the metric is no more Schwarzschild-like but something more "regular" or Minkowskian again. This model is widespread in effective quantum gravity theories.