Hi Luck,
I might understand your problem. That datasheet is not very updated, so if you would like more info I recommend searching for newer devices with the same specs; take TRS202E just as an example.
Nevertheless from the picture below, extracted from the old datasheet, you can clearly see that the receiver has an internal pull down resistor, this allows the Rin pin to stay floating. Whereas the Driver doesn't have any internal pull up or pull down resistor, so we recommend to not leave the driver inputs floating.
As a matter of fact, the driver inputs are directly connected to the gates of the NOT gate, by leaving that node floating you would have an unpredictable behavior of the output; most likely with some leakage current.
Please let me know if this clarifies your thoughts.
Best regards,
Adrian
