QuoteI don't think so. I make a peanut butter gianduja for which I stir tempered chocolate into peanut butter, but I also sometimes melt down the scraps and re-temper them and the result is the same. It's all about the cocoa butter.
Other fats and oils soften cocoa butter, and the more you add, the softer the mix is and the lower the temp you need to work at.
Same with you ... in my tests, I haven't seen any noticeable difference as well ... but Peter Greweling, Ewald Notter and some other chocolatiers in the recipes in their books always use melted chocolate and are tempering gianduja at the end of the process. Maybe it is just a habit coming from producing gianduja in bulk quantities with big melangeurs.