HarvestCraft's raisin recipe only supports harvestcraft grapes, instead of using cropGrape. This seems like an oversight to me because other grape-based recipes added by HarvestCraft, such as grape juice and grape yogurt, use cropGrape instead.

Would it be possible to improve this recipe?

Thanks!

You can change this with MineTweaker I believe until it gets released if you need it badly.

Or Craft Tweaker

Fixed in 1.12.2 along with all the other previous smelting recipes