They didn't - but the point is nobody even noticed the change in design, construction and materials. However - remember that your 'fact' is actually incorrect. If you measure any material few are absolute reflectors of all frequencies in the audio band are they? Egg boxes, even the old ones do have a measurable absorption and reflection component. Tiny of course, but they do actually do something. In fact, they are actually diffusers in practice - so offering a distinct and measurable acoustic fingerprint. Please - before you explode, I am NOT saying they're good, we all know they offer very little - but can you be certain the new ones are not better? That's my point in starting the topic. Do new biodegradable and green friendly trays work as sound treatment to a degree that makes them worth trying?
Seriously = I thought about trying a wall in my video studio - but I have discovered a very important caveat - the damn things catch fire very easily. I guess the air trapped inside makes them pretty dangerous? I've not tried to test combustion on a Chinese foam tile. Maybe I should?