Well it was a creative design decision to make. In Star Wars these fantasy technologies are poorly understood generally. Though in SW lore we have "ray shields" that are designed only to stop the colorful bolts fired by the various guns in the galaxy (but not unlimited protection obviously) and "partical shields" that are designed to stop physical impacts like missiles and collisions. A ship could conceivably have both, but that doesn't mean it would be invulnerable. Shields have limits. But a game developer has to make choices based on how they want the game to be. Do they want people to favor one style of play? Do they want to make it "fair" or "fun"? What is "fair" or "fun"? Is it challenging? Is it balanced? Does it encourage using all the different units or favor certain ones? etc.
I imagine the gameplay wouldn't change that much from the demo to the full version, but who knows. This isn't a beta test though, so I imagine it would be pretty similar. However multiplayer might be completely different.