Please refer to the Technical Reference Manual(TRM) I am attaching along with this response. Please refer chapter 8 in TRM how CY7C68013A is buffered.
Q)What exactly do you mean by overflow ?
A)I assume you are referring to the scenario where the data stream is faster than host requesting the data.If yes then there is chance of loss of data.
I believe you have created a Tech support case. We will continue to interact in the case.