The problem with too-hot chocolate isn't the ganache melting, it's just the coating itself is very unstable and never hardens properly and is usually too thin as well. Too-hot chocolate sometimes slides off the ganache too.
You can certainly use chocolate molds, but they're way more work. Terffles are formulated to be formed by hand, which is easier. If I ever explore molded chocolates I'll use softer, more liquidy fillings, because I can't do that now.
