Wing Loading is only proportional to scale or really the same design. You are comparing a quantity of (Weight)/(lenth^2) . Weight is equal to (length^3) because of density. The numerator will increase much faster than the denomonator when scale is increased.

I also say design because The EF yak also has a flying tail and a wider fuse than the UCD 60. If you ever took a class on aerodynamics you will also see that the Lift/Drag Ratio of a tapered wing is greater than a rectangular wing. I have that equation if anyone wants to see that.

Comparing the airplanes Wing loading is only a good back of the envelope calculation, nothing more. In aerospace a lot of equations are made based upon asumptions, rounding/estimating and excluding smaller terms from equations just so we can solve them.