Hi SPDevOne,
After you set the current user as a Default user in People picker field, by clicking on the People picker control before saving the data, could you save the People information to the list?
Per my certain knowledge, when an Edit form control is in New mode, however, the Item property is ignored. The form doesn't show an existing record; instead, the values in each field match the default values of the data source with which you configured the form.
So though you have set the current user as a Default user in People picker field, the value in this field might not match the default values of the data source. So if you don’t click on the People picker control before saving the data, the data cannot be saved to data source, and you are asked to enter a required value to the required field.
For People picker field, on Edit screen, you could search a user by entering user name, then select one from drop down items.
About Edit form and Display Form, please check this documentation for more details:
https://powerapps.microsoft.com/en-us/tutorials/control-form-detail/
Best regards,
Mabel Mao