It says on the back of the label that this yarn must not be used along with the original 1 ounce balls.

It is not the same - it will go further than previously. If using these 20 gram balls with one of the patterns for the original yarn, it is necessary to go up one needle size to get the same tension.

The later patterns intended for use with this yarn do not include New Pack with the yarn name, but show the new ball size of 20 grams.