And here is the same thing, version 2016, showing the desired effect.
Layered Plan Sample 2016.layout (174.7 KB)
I produced this file by saving the 2017 Sketchup model to 2016 format, and then recreating the layout in Layout 2016.
Interestingly, if I open this 2016 file in 2017, the countertop shows correctly. So now I know 2017 is capable of displaying transparent layers.
Another test: In Layout 2017, I saved the first file down to Layout 2016, and then opened it in 2016. The countertop is opaque.
And one more test: I created a 2017 Layout from the 2016 model. The countertop is opaque.