Here are my thoughts but others may have a different take. You boil hops in wort for an hour to extract the bitterness from the plant. Beer is essentially sweet and the bitterness offsets the 15 or so points of sweetness that is left when the yeast quit fermenting. With wine, yeast quit when there are no simple sugars left and that generally means when the wine is brut dry. So, do you really want to have all that bitterness with no sweetness as a counterbalance? You might.. but you might want to highlight the flavor of the hops. That's a 10 minute boil. Or the aroma of the hops and that's a dry hop - adding the hops to your secondary for about a week to 10 days.
The other thing is that cooking any flower or leaf for 60 minutes is a little bit of overkill. Do you drink regular tea? How long do you boil the leaves for? Do you even boil the leaves? You steep the leaves in water a little below boiling for about 5-10 minutes and that extracts the desired flavors. Trying tasting black tea after you boiled it for 60 minutes. You are chewing on tannins. Hibiscus may be different (doesn't have all those tannins) ... but stewing the flowers for an hour in boiling water? Your call, of course.