The W7500P reference design is a standalone implementation. As such it is unknown what will be driving the board (MCU choice). In this case it is prudent to provide a good level detector for Power On Reset to ensure the reset state of the device when power is applied or during power failure/return.
The WiZWiki-7600P development board has a MANUAL reset switch (Sheet2-D1) which assumes human presence to reset the device should it fail to initialize.
While perhaps acceptable for a development board this is not adequate for a finished product expected to reset gracefully and predictably for power on or power failure.
If you have an MCU with POR detection built in, or added to it, you can use this to reset your WizNet 7500, but you should ensure predictable reset conditions for you product.
There are a plethora of PMIC power supervisors to chose from, do yourself a favor and put one on your board. Many of these POR supervisors are SOT23 packages, so at the very minimum you should layout one on your board even if it's a DNP placeholder.
Be careful during part selection that some are active pullup and some are open Collector/Drain outputs.