I think most of the string players polled, being professionals, have been trained to attain a certain 'modern' (post-1800!) concert hall sound, that will fully utilise the music written for them from the Romantic composers onwards.
As well as major modifications to the violin's construction, e.g. angle of neck and changes to the bass bar, strings and bridge, this requires using the Tourte model of bows, which work and sound in a completely different way to the older Baroque and transitional bows of the 18thC.
Because of these changes to the music, the instrument, and the requirements of larger orchestras and halls, the player will perceive a 'need' for a modern, clean, masculine sounding instrument, and when she hears that sound will identify it as desirable and therefore it must be the Strad, mustn't it? Usually wrong.
It would be more of a fair comparison to factor some of those variables into the tests.
Recordings of some of the greater players, playing older instruments, reveal that they are content with, and desire, a warmer, human sound from their instruments.
Once you stop looking for the 'perfect' 'clean' note, and start listening for the more intimate, over and under-toned 'feminine' quality of sound it becomes easier to pick out the older instruments. There are several similar blind comparisons if you Google for them, and I can spot the older sound usually within the first bar or two.
Maybe that's because I'm not classically trained yet play a bit of Baroque alongside my fiddling.