I'm not sure why cats respond to foreign objects being put on them by not moving, but it seems to be their default defense.
For me, playing with Construx was formative for two reasons:
(1) I had my first encounter with gender stereotyping when a neighbourhood kid told me I wasn't supposed to play with them because I'm a girl (I did anyway--I loved and still love building things), and
(2) I realized that the "from Santa" sticker on the bottom of my Construx tube was written in my mother's hand. I immediately confronted her with the evidence and she told me not to tell my sister. My disappointment with there being no Santa was mitigated by the fact that I figured it out by being sleuthy.
These toys were awesome. I made a big jeep for my GI Joes to ride around in, a gun, and some other great stuff with them. I'm so glad Children's toys actually involved creativity and didn't take a shitton of batteries back when I was a kid.