That is what I was told when and I started and I still use.

I always use Konah black, not the fake one at JoAnn, the real Kona by Robert Kaufman.

My quilt shop lady recommended a black fabric by Timeless Treasures and color is called Jet. It is a black, black. I prewashed with a color catcher and there was no bleeding. I really like it a lot.

I found a bit of TT Soho line in black. Beautiful and with a good hand. Unfortunately, not enough for my needs and was told they are not making that line any more?? Bummers. Then I found a really nice Red Rooster black. Again not enough for my quilt. Was told the reason it felt and looked better was because of the higher thread count/psi. Used MM black but was thinner the last time I used it so the hunt was on for the next best. Haven't felt Northcott but really love their fabrics and now a store close to here is carrying their line so that is my next stop on the quest for the best black.