There's also a distinction to be made between the questions "does a Stradivarius sound different than a modern violin" and "can a performer successfully identify a Stradivarius?"
Supposing that a performer does not in fact know what a Stradivarius sounds like and is unable to determine which violin is the Stradivarius does not mean that the Stradivarius does not in fact sound different from a modern instrument never mind which one of those sounds "better".
(I believe there was also a problem with the original test that I don't know if they addressed this time around, which is that it's pretty hard to get permission even to do things like change the strings on a very old violin. So, if they're testing a Stradivarius with old strings against a modern violin with new strings, that's not exactly a fair test.)
Supposing that a performer does not in fact know what a Stradivarius sounds like and is unable to determine which violin is the Stradivarius does not mean that the Stradivarius does not in fact sound different from a modern instrument never mind which one of those sounds "better".
(I believe there was also a problem with the original test that I don't know if they addressed this time around, which is that it's pretty hard to get permission even to do things like change the strings on a very old violin. So, if they're testing a Stradivarius with old strings against a modern violin with new strings, that's not exactly a fair test.)