I'm not being "disingenuous", yes, I had to look it up to make sure I knew what this means, because it's true. After vocals, the next most-unique instrument is the guitar, and it's not very far back at all, it's pretty much riding the bumper of the vocals.
I also said "great" guitar players (ie. JP, Vai, Gilbert, Satch, Bettencourt, etc) and not Jonny Powerchord since the great players strive for the ultimate tone and in doing so establish what "they" sound like over any other players out there.
I'm sure it's obvious for guitar players out there, just like drummers can identify drummers by their sound/style, but I can't since I'm not a drummer and don't know the nuances like I do with guitar. It's also why on TV (ie. The Voice) nobody cares about the band at all (which is a travesty), only the vocals, since everyone has a voice and can relate, but not everyone plays an instrument... which is why, for many new listeners to DT, they can usually decide right away if they want to hear more based solely on LaBrie's vocals, and why so many people say "I'm sure it's great, but I can't get past the vocals."
Anyway, off-track a little, but in the end being nitpicky over some pre-recorded background vocals or how the same singer shouldn't sing multiple parts in-studio, seems silly to me.