The bad is they want me to mail in the extra #2 backstrap to exchange it for a #1. I'm not sure that is worth the hassle.
IF you actually would use that #1 Backstrap, then yes, it's worth it.
IF you feel the need to have a complete set for the Pistol, then yes, it's worth it.
IF you are comfortable with the Backstraps you have and only use one of them, then probably not worth your effort. Just shoot it and be happy!