Kind of an old post but i'll add some info for any one stumbling across this.
As i'm aware and have recently tested, the 'additional scripts' only fire on the 'order confirmation page' AFTER you've checked out. It does not fire on the actual checkout page where you enter all your info. You can test this by adding your console.log in the 'additional scripts' and then simply placing an order and wait for you to reach the 'Thank You' page. You'll for sure see it in the console.
If you're on Shopify's basic plans you cannot edit anything on their checkout page, unfortunately. If you wan't access to this page, you'll have to upgrade to their Shopify Plus plan. There you'll have access to the checkout.liquid file that you can modify.
Hope this clarifies a few things.