Yes, adding a requirement that the decks may not be considered independent for evacuation would significantly affect the test.
So would, for that matter, concealing the cameras that monitor the "good" exits (have they done that yet?), or filling the aircraft with unsuspecting passengers instead of semi-trained personnel.
But, well, that's not the point. The test, like many others, is artificial. It doesn't simulate real world conditions any more than a Blood Alcohol level tells you how well someone can drive: if it's .20, they can't drive; if it's .04, they might be perfectly good drivers, or they might be horrible ones. But, like the BAC it is an objective benchmark that can be used for making safety determinations. Unlike the BAC, however, it's a benchmark that seems to get more generous with each generation of aircraft. That does not make the planes "less safe".
Didn't it use to be 45 seconds?
Anyway, inspite of what those of us who see those upper-deck slides snaking down and around the lower-deck ones, even if this broken leg and uninflated slide meant a test failure doesn't mean serious safety problems (yet). But, no offense to the mad-dog, bringing up the MD-11 as similar example in terms of safety won't appease the "Skytanic" crowd. The MD-11, along with its DC-10 heritage, could be argued to have dealt the final blow both to its manufacturer and an airline on its perceived lack of safety. The Airbus people cannot afford to build an 880-seat MD-11.