What is your definition of cold reset?
You should assert the RTC_PWRONRSTn input along with the PWRONRSTn input the first time power is applied to the product, but you would only assert the PWRONRSTn input on subsequent power cycles if you need the RTC to maintain time.
The RTC crystal oscillator is disabled by default after RTC_PWRONRSTn is asserted.
Regards,
Paul