Yes, you need to wait. With all winemaking kits, always do the last thing, i.e., if it's a choice between a gravity reading and a date, and the reading is low enough, wait until after the specified days. If it's at the specified days and your gravity isn't low enough, keep waiting until it is.
Yeast does more stuff than just ferment out sugar. It also produces ketones, esters and aldehydes during fermentation and then re-absorbs or converts them afterwards. If you rush it, you can leave your wine rough and green tasting forever.