The doggo decided to check for the presence of a door before entering the room. We can see how the good boy touches the alleged door with his paws and only when he assures himself of the safety of his path - he runs into the room to greet his hooman. This clever pupster took these precautions just a few moments after his brother barreled into that very door, so it looks like he learned from his bro's life experience.
"When you saw your brother run into the screen door just a few moments ago," the caption under the post says.