Data transfer using VPP in U(SIM)?

I am confused about the nature of data transfer through the VPP pin of U(SIM) (pin C6) which is connected to SIM_SWIO (pin A4) of the Reader.
How can a VPP pin transfer data ?
Even if this is a typo,then
Also, How is the U(SIM) operating in this design while only VPP connected to the Reader and data pin of the U(SIM) connected to SC60?
The design I am referring to is

VPP:programming voltage, //the SIM card’s programming power.In general it is an empty pin in a circuit.
I hope the following documents are helpful to you.
Quectel_SC60_Reference_Design_V1.2.pdf (1.1 MB)

I am still confused.
Shouldn’t the VPP pin should be connected to the voltage ?
How is it transferring data ?
How can a voltage pin be used to program the (U)SIM (or anything, for that matter)?

you are great! USIM’s VPP pins are not normally used (or dangling pin), so if you have an in-depth understanding of USIM’s VPP, please download the link file and look at it in detail.