Attribute is not getting populated for delimited application in IDN

Hi,

We have a delimited application where we have defined our schema as below-

WE have created provisioning policy where we have mapped the ISID to Sailpoint uid identity attribute.
We are doing an account creation request where we can see in the accounts all the attributes are getting populated as expected except ISID. Below is the account request-

Below is the IDN account details-

As ISID is the native identity, it is populating account ID but why it is not populating ISID. I understand that for connected application the Get-Object populates the attributes back but here that is not the case.
We don’t want to fill manually the data and import.
Is there any way to handle this?
@colin_mckibben @chirag_patel - Any suggestions?

I don’t think there is any solution here.
Thinking of real world use case, you must be aggregating your source in some interval right? in that case this value should get populated in next aggregation.