Look at it this way.
Suppose you quickly brown a pork tenderloin in a pan using high heat then remove it to a CLEAN plate while you sauté some apples. Then you return the pork to the pan.
What do you do with the undercooked, potentially contaminated pink juices that have collected in the CLEAN plate?
I add them to the pan before putting it in the oven. After watching decades of cooking shows on PBS and Food Network, I can attest that all TV chefs do as well.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan