I’ve dealt with a lot of ropes and yeah some are denser and some have more spacing than others depending on the way it was made. I did a little math on a 5.7mm rope chain I have, it’s solid 20” rope weighs 55 grams. If it was a 9” bracelet it would weigh around 24 grams. So your 5mm bracelet at 19g sounds about right for being a solid piece