Hmmm...that wouldn't be an example of what I call "twee voice syndrome".
To me, twee voice syndrome bears the mark of on, sometimes two specific characteristics.
First, any maudlin, over the top use stilted emotion in the voice. Men do this much more than women, and I would argue that is more likely a problem with Dick Gaughan's voice than Mary Black's.
The second characteristic is to be found exclusively with the female voice, and the modern folk aesthetic that says a woman's voice for trad music should high and wispy, like what's her name from Altan (cringe). Give me Maddy Prior, Dolores Keane, or Sandy Denny any day!
However, that is not to say I don't like the soprano voice in women singers, as I do. I just like a high voice with clarity, rather than the wispy sort of voice, which always sounds strained and tinny to me.