Also, plant many... It is a survival advantage if different seeds from same plant will yield plants with different growth rate and other such characteristics.. That way, if for example some of the plants are slow growing and others fast, maybe if a caterpillar comes it eats the fast growing, but the slow growing will survive, or the inverse, maybe the faster growing will be able to reach the sunlight while the slow growing will end up being buried due to different movements on the surface shifting the soil. Or some might be slightly more drought resistant while others more cold resistant, etc (just random examples but you get what I mean).

So sprout many different seeds, and you'll see some will thrive better than others. I had maybe 10 sprouted acuminatas almost 5 years ago, now I'm left with 2, one is quite small and the other looks beautiful and healthy. All were grown under same conditions.

I have 2 floribundas from seed sown in March. One, west facing with a slight southern tilt, was completely stripped of phyllodes by slugs in May, it grew back quickly when the dry weather set in, and now has a few branches 2ft long. The other is growing in a marginally less sunny position (east facing with a slight northern tilt), didn't get slug damage, but is only 2-3" tall. It may be environmental factors, or differences in the size of their root systems, but I wouldn't be surprised if genetics played a major role here.

A acuminata narrow leaf