Why was the training of UniAD without validation

[rujiao]

Facts:

1. According to the paper, the performance of UniAD in comparison to prior state-of-the-arts was tested on the nuScenes validation
   set.
2. According to the training log in release 1.0 and 1.1, both test set and validation set are set as nuScenes validation
   set. The evaluation ran only once based on the metric in the end after 20 training epochs.

Questions:
-Why was the training of UniAD without validation (loss)?
-How do you know that training for 20 epochs is not involved in a early stopping or overfitting?
Thank you!