Sadly If you follow kit instructions to the letter, you are more likely to be drinking beer that was fermented at too high temperature, bottled too soon, and not conditioned for long enough time, all geared towards claims that you can be drinking your beer asap to hook people in. Most experienced brewers ignore the instructions, and for new brewers on here the usual advice is to follow the 2+2+2 rule which gives newbies a fighting chance of producing something better than just drinkable.Following the instructions is absolutely key, but packets of yeast tend to claim you can just sprinkle the dry yeast onto your wort. You can, but you won't get the vigorous fermentation that you'd get if you made a yeast starter first. That's a pretty easy thing to do. You just need some dry malt extract and a container. It makes a big difference.
And personally when I did kits I usually sprinkled the yeast, but sometimes hydrated before pitching and apart from noticing little difference in the speed of fermentation start, it made no difference to how the beer turned out. However if you have one of Muntons kits with the miserly 6g packets (assuming they still do that), it might well be good advice to build up the yeast since 6g has been known to produce stuck fermentations, as many on here will confirm, including me.