If you mean OG and FG numbers need to be provided in the kit, then I say Not True.
The hydrometer is what you use to to determine your specific batch's OG and FG values. And if you look at the larger kits, both extract and all grain, all they really give you is an estimate of the OG. (No FG) Granted, for extract kits OG estimates are pretty much spot on, but for all-grain recipes, the brewer's efficiency can have a significant impact on OG, which is why it's often referred to as the "target OG" it is quite common for all-grain brewers to have OG readings several points off the target. My last brew, a 3-gal all-grain, had a specified target of 1.060, but I measured 1.070 in the fermenter because I did better than the estimated 75% efficiency.
I believe they don't provide OG numbers so as to make the kits less scary for new brewers. While collecting, and using the numbers is pretty easy, understanding them is a little harder.
What's "not good" about the answers in other forum posts?