Hi all,

I have noticed that my 380SE, when facing steep uphill, will not roll back if it's in drive. I am not talking about that idle-in-drive forward force, but rather if you let go of the brake, the car will roll back a little then stops, feels as if pulled the hand brake. I don't remember my previous cars would do this, and tried another car (auto) the other day on the same hill and it would roll back.

Is the car purposely designed to do so, or unintentionally, just the nature of the design? Would anything be damaged (or shorten component life) when doing this?

....
It's just the way your car is... it's simply for force of gravity and the angle of incline against the weight of your car and power of your engine.
It's normal... but don't let the car roll backward when it's in a forward gear, that's not good for it.