No, it's not true. Sunflowers need full sun, and are extremely easy to grow by direct sowing. The easiest way is to just chuck the seeds on the ground in the area you want them, if you have lots of seeds. However, when you buy special varieties, you sometimes don't get that many seeds in a package, so it's best to plant these purposefully (that is, place the seeds down and cover them thinly) to make sure they don't get washed away or eaten by birds. At the end of summer, just brush the seeds out of the dry seedhead and scatter the seeds for next year.
Lori