No it's not an "inferior" way of brewing at all, it's actually the MOST COMMON way of brewing around the world. That's how most extract kit instructions go. Because most folks starting out don't have the capability yet for doing full volume boils. That usually comes much later.
Many many many great beers are made on the stovetop.
Brewer's best kits are some of the best beginner kits out there. many of us got started with them.
If you have the capabilities to brew full volume, then do so, but doing it the way the kit says, doesn't mean it will make for a bad beer.
You'll find in this hobby that there really are many different ways to do things, and that "better" or "Worse" are simply best replaced with the idea of what I prefer to do...