I'll contest that point. I've built 5" guns that weigh and balance the same as a 4.25" shorty.
The key difference being that the longer gun always shoots softer.
Help me to understand this. In these cases would you say you lightened the slide equally as much on both the shorty and full size? I mean, it just makes sense that a gun with 3/4 of an inch less real estate would weigh less assuming everything else is completely equal.
The shorty slide gets 3/4" lopped off and a few serrations in front.
The 5" slide gets many more serrations and some internal lightening in the front end. Couple that with a spiral fluted barrel and possibly an aluminum guide rod and you have a package that weighs and balances the same as a shorty.
You can get a shorty slide to weigh too little. It's all about balance.