Too reflective, like a flat mirror, will send the light off in a random direction rather than back as the detector. Worse yet, things like double reflections can result in timing errors as some of the signal follows a longer path. You want a target that is nicely reflective but not so shiny that you get any double reflections. The ideal is a matte surface painted the same color as the laser.

Ah it relies on diffuse reflections to guarantee some light returns to the sensor but specular reflections mean none is returned.

This is a good example of why sensor fusion is good.