It's all MAME fault.
Instead of saying on their splash screen: "Use of ROMs is illegal...blah, blah".
They should have said: "These ROMs are abandonware, they are not sold and copyright holders do not exist. We provide all the ROMs here for free and if there is someone who would like to claim a copyright please step forward to prove it, inform us where can we buy the game and if requested we will be happy to remove the game from our emulator."
That's what they should have said, and everything would have been different.
The MAME devs correctly stated the law. What they listed is not an "interpretation". If they listed your proposed language it would not have altered the law one iota and could have compromised the project. What is the legal stance on abandonware again? Oh that's right, it doesn't exist. Failure to locate a copyright holder does not constitute permission to recreate the product.
Perhaps, but playing stupid is a valid legal tactics, I think it would work for the best, especially if they were still based in Italy or some country other than USA.
The thing is, the developers of those games, those people who really matters here, rather than companies they worked for, they would prefer those games are out there. Playing them still after they can not be legally bought should not be theft and no one should feel like criminal because of it, but rather emulating and providing them is a tribute and appreciation, like we all can listen to classical music today and no one has to buy the notes and composition books or pay any copyright for it to anyone.
The point is to somehow enforce companies to say out loud and make their position official, black on white. I believe that's what Nintendo did and some other companies regarding some specific games, but there is still majority of the games for which the companies that made them really DO NOT EXIST, there is simply no one to claim copyright, they are gone, like Ludwig van Beethoven, but that should not stand in a way of us appreciating and paying tribute to those games, by actually playing them and making them available out there.