Before revision:  However, the effective representations offered by the models target at each token inside a sequence rather than each sequence and the fine-tuning step involves the input of both sequences at one time, leading to unsatisfying representation of each individual sequence. Besides , as sentence-level representations taken as the full training context in these models, there comes inferior performance on lower-level linguistic units (phrases and words).
After revision:  However, the effective representations offered by the models target at each token inside a sequence rather than each sequence and the fine-tuning step involves the input of both sequences at one time, leading to unsatisfying representations of various sequences with different granularities. Especially , as sentence-level representations taken as the full training context in these models, there comes inferior performance on lower-level linguistic units (phrases and words).