In all our RVs, I've never seen a gap larger than 1.5" at top and bottom of internal doors. I always figured this was cheaper than a door vent for ventilation and might also be a flex cushion.
If you have a gap that much larger, I would find another model/brand like yours and see if the gap is uniform. Maybe they gave you the wrong door?
If not, I would probably just mod the door. Take the skins off, extend the frame, and replace/mod the skins. There really isn't a whole lot to these doors. The frame usually has a joint nail in the corners, and the skins are just glued on as well as the styrofoam used in the middle. I've had to rebuild several doors when the glue gives out in about four years
If you don't want to go to that much trouble, just hang some fabric or rubber material from the bottom of the door. Wallah, privacy
Scott and Liz - Southern NM
2012 Wildcat Sterling 32RL - w/level up (best option ever)
2007 Chevy 2500HD 4dr short bed Duramax w/allison
Reese Fifth Airborne air ride king pin coupler with Sidewinder