It seems to me, that if they had followed your suggestion, the astronauts may be subject to a lot of solar radiation within the space stations. Although what percentage of reflectivity an opaque plastic would have, I am not certain. I hope not a black opaque plastic bag, as you will surely burn up as the black absorbs all the radiative heat.

Granted, I'm talking about the reflective surface pointed outwards, in this example. However, it is still pertinent for the inside of the tent, if that's what you want.