I took the 'different in each case' to apply overall between each unclued light, not within them, nor to each constituent element of the common feature. So my assessment would be OK, as long as another unclued wasn't similarly possessed. Too much messiness otherwise.
As others have said, I think the preamble omits to say to ignore two acute accents (in 26D and 42A), but perhaps doing so is passe. Apart from the uncertainty about what "different in each case" meant, I did find the preamble unclear in a couple of other ways:
1. Not knowing whether "two paired words" means 2 words or 2 x 2 words.
2. Not knowing whether the characteristics of the unclued lights as described were mutually exclusive (they're not - one hyphened applies to two paired words).
But not fully understanding the preamble until the puzzle is virtually solved is not necessarily unreasonable in my book - it can (sometimes) be part of a good endgame.