We signed Johnson to sit on the bench.
Fabbro is a not a fine #4, if he was, he wouldn't have been waived by a bad team.
He was a 3rd pair guy the last couple years before they demoted him this season.
I'm sure Preds tried to move him for a ham sandwich and got no takers.
Unless he has a miraculous turnaround, I doubt he'd fetch more than Zamula.
I'd rather Fabbro play Johnson's role than Johnson, especially seeing as Johnson has already played 10/15 games over the many suitable candidates you're citing in LHV (and I don't know who you are considering that to be honestly).
And as far as flipping, even if he is a 5RD, you're going to get someone giving a 3rd or 4th at worst at 50% retention.
Just feels like a missed opportunity to get a little extra value in the margins.