Planned Start Date field on the Release form is getting populated with a random date on creation when it should use the current date and time instead.
This is expected behavior.
When a Product record is associated with the Release by the Parent field, the Release form's Planned Start Date for the new record will take in the date from the Product record.
If the Product is not associated to the Parent field, the Current Date and Time will be used instead.
This behavior only happens when the record is created. Adding a Parent will not change the Planned Start Date after an existing record is updated.