That’s about recording outputs from the Prime 4. Not recording external inputs into the Prime 4.
The title is “[Prime 4:-Record a full DJ set to any connected source]”
Not “[Prime 4:-Record a full DJ set from any connected source]”
Again, straight from the product page : “Record a full DJ set to any connected source”
Edit: Sorry for the edits. Accidentally deleted the post and tried to revert it… Too much preworkout today.