8.4Why this matters

Bad deployment process:

developer checks out code

changes:
salesforce.url = QA

deploys

later edits code:
salesforce.url = PROD

deploys again

This creates risk that:

QA credentials go to PROD
wrong database used
wrong Salesforce org updated
config differences aren't versioned correctly

Better:

one application artifact
        ↓
DEV configuration
QA configuration
PROD configuration

Interview phrase:

“I prefer immutable application artifacts promoted between environments with environment-specific configuration injected at deployment time.”

That's a strong DevOps/integration answer.