Wio Terminal Battery chassis 650mAh diagram question


I’m trying to understand how the Wio Terminal Battery chassis works using the schematics and I have a question about the BQ25606 charger and the way you are using it.
Maybe I’m wrong but, what if the TI BQ25606 actually negociates more than 5V with a USB High voltage adapter ?
The VBUS is used to provide energy to the Wio Terminal when it’s charging because the BQ25606 does not provide any voltage when charging the cell (no boost), so up to 12V could get into the circuit (USB HV)
I know there is a fuse and zener diode for protection but I don’t think this is the way to prevent this to happen.