ESD Protection Diode: I/O Protection on VBUS Line instead?

The ESD0524 part is rated up to 5V. So based on that only, it should not be used for VBUS which might be up to 5.25V. Having said that, the datasheet has breakdown rating of 6V and the example uses the part for HDMI 5V supply and Hotplug protection, which are also lines that are allowed to go at least up to 5.3V. So while it is meant primarily to be a low capacitance ESD protection for high speed data lines, it can be used for power line protection, it just is not optimal for it.

USB is positive signal voltages only. Vcc maybe On or OFF depending on the controller but it is positive if ON. TVS (Transzorbs) are bi-directional and meant for very short transients of either polarity.

Zeners are often better when signals and power are of a single polarity. Zener diodes are built with more junction mass to tolerate more than just surges, they can clamp continuous over-voltages as long as current is limited. Also the reverse clamp is less than -1 volt and forward clamp should be close to 5 volts, though for some head room a 6 volt clamp is common. TVS diodes have the same clamp voltage in both directions, exposing the IC pins to as much as -6 volts.

To protect power the zener should be more beefy. There is no capacitive loading issue on power feeds so a dedicated SMD zener of 5.1 volts to 6.2 volts can be used. On the data lines you need to use ultra-low capacitance TVS diodes or zeners, or you will not get USB 3.0 full speed to work.