If the 2 scales are in parallel, i.e. both connected to the weight and ceiling, yes, you would be reading 5 lbs each. If you connect them in series, the bottom one will read 10 the top one 10 plus the weight of the bottom scale.I'll try it this way. Take a spring scale. Hook it to the ceiling. Now put a 10lb weight on it. It reads 10lb. Now hook a second spring scale to the first and again put a 10lb weight on it. Each spring scale will read 5lb. One cannot concede any force to the other in either direction, they distribute the force evenly. The two strainers are doing the same thing. That's what I'm trying to say.
You probably think the mass is just shared between the 2 sides (so you are thinking the scales are "in parallel"), but you are neglecting the fact that the mass is negligible when compared to the tension created, so the system is more "in series"!