The using of golden dataset in Augmented SBERT Training

Question

I use the training strategy of Augmented SBERT (Domain-Transfer). In the code example they use the golden-dataset (STSb) for the training evaluator. Here two code snippes of the example of sentence-transformers:

Get data and split them

gold_samples = []
dev_samples = []
test_samples = []

with gzip.open(sts_dataset_path, 'rt', encoding='utf8') as fIn:
    reader = csv.DictReader(fIn, delimiter='\t', quoting=csv.QUOTE_NONE)
    for row in reader:
        score = float(row['score']) / 5.0  # Normalize score to range 0 ... 1

        if row['split'] == 'dev':
            dev_samples.append(InputExample(texts=[row['sentence1'], row['sentence2']], label=score))
        elif row['split'] == 'test':
            test_samples.append(InputExample(texts=[row['sentence1'], row['sentence2']], label=score))
        else:
            #As we want to get symmetric scores, i.e. CrossEncoder(A,B) = CrossEncoder(B,A), we pass both combinations to the train set
            gold_samples.append(InputExample(texts=[row['sentence1'], row['sentence2']], label=score))
            gold_samples.append(InputExample(texts=[row['sentence2'], row['sentence1']], label=score))

Initialize evaluator and fit model

logging.info("Read STSbenchmark dev dataset")
evaluator = EmbeddingSimilarityEvaluator.from_input_examples(dev_samples, name='sts-dev')

# Configure the training.
warmup_steps = math.ceil(len(train_dataloader) * num_epochs * 0.1) #10% of train data for warm-up
logging.info("Warmup-steps: {}".format(warmup_steps))

# Train the bi-encoder model
bi_encoder.fit(train_objectives=[(train_dataloader, train_loss)],
          evaluator=evaluator,
          epochs=num_epochs,
          evaluation_steps=1000,
          warmup_steps=warmup_steps,
          output_path=bi_encoder_path
          )

First Question: Why is the golden-dataset used for the evaluation, if the model fits on the silver-dataset?

Further, the test_sample from the golden dataset is used for the final analysis:

# load the stored augmented-sbert model
bi_encoder = SentenceTransformer(bi_encoder_path)
test_evaluator = EmbeddingSimilarityEvaluator.from_input_examples(test_samples, name='sts-test')
test_evaluator(bi_encoder, output_path=bi_encoder_path)

Second Question: Why is the test_sample based on the golden-dataset? Why is the test_sample not based on the silver dataset?