How data priority works for Salesforce Integration App?

Hi,

We'd like to resolve trouble for CRM Integration, where some specific contact field data for a certain contact were not synced and updated to Eloqua contacts from Salesforce.
We suspect our data priority settings are wrong, and need to understand more about how data priority works in combination with Salesforce Integration App.

In order to narrow down possible points to fix, we'd appreciate it if you could answer the following question, which are based on our situations.

Question 1.
As a starting point, is this general guidance below is still active? I mean this is about Salesforce Integration App, instead of legacy Native Integration.