I can not tell you right or worng, but i do make good Red muscadine wine, my grandmother made very good muscadine jelly, i used to help her and get my juice the same way,hi heat boil them in water and mash well with a potato masher,bring heat down to "med hi"and stir enough not to burn the mash on the bottom of the pot. a trashey looking scum will form on top while boiling spoon it off, when it stops scumming, cover and let it cool to room temp.i strain and press out the juice with old teeshirts.
1/2 gallon of muscadines cooked down like this will make a very concentrated juice,add 4 cups sugar, top it off with water to make one gallon. repeat as needed to fill fermenter. 1 mounth later rack to a 2ndary, very tasty in a nother mounth.
works for me.