Any organic crud above the trap can end up smelling. What are your pipes made of? Smooth plastic makes it harder for the crud to adhere. Soaps, oils, skin flakes, hair, anything that is above the trap can and will likely start to smell. The shorter the fall, and the higher the water level in the trap, the less surface area. You could use a bottle brush to clean things after removing the shower grate.
Note, a common shortcut when building a shower is to install the liner flat on the floor. This in itself can lead to mold buildup in a shower. The tile is not the waterproof layer people think it is...code requires a waterproof liner that is SLOPED underneath the tile, not flat on the floor. It is the primary waterproofing...the tile is decorative. If your liner is flat, eventually, all of the cement under the tile will end up being saturated. After awhile, the pH will change with the pollutants from soaps, etc., and that plus the moisture will make the shower start t osmell like a swamp of rotting organic material.