LOL, olliecollie!
You made his day! Dogs love to think that they, and they alone, are responsible for chasing off the paper boy, the UPS driver, and other “dangerous interlopers”.
My daughter has a little 9 lb. Bichon Frise, and the highlight of her day is successfully scaring the mailman off every single day. Little Bijou knows just what time the scary man is going to come, and gets up on the back of the couch, little growls at the ready.
As soon as the mail comes in through the slot, she is in full attack, and gosh darn, if she doesn’t chase him away every single time. She is so proud of her little “inner beast” when he politely leaves, and is sure she is totally responsible for saving the household from such dangerous characters!
Your scotch terrier probably had similar delusions of grandeur. You made him feel so important!