Seedling stretching: genetics or lack of light

Yes, different varieties stretch different amounts. Many breeders list the stretch in the plant's description. Your plant looks pretty normal. There is often a relative long stem before the cotyledon leaves. Keep an eye on your sprout and you should see that the spacing from the cotyledon leaves to the first set of true leaves is much closer.

All genetics are different and then you have phenos (DNA from the parent) to take into account as well. I have 4 different strains on the go at the moment and one plant is 1.5 inches taller than another, yet both seem healthy and happy. That picture does look a bit like stretching though and you have a bit of a lean going on as well. Try lowering the light or increasing the intensity if you have a dimmer switch. Rotate the pot 180 degrees each day as well so it will encourage the seedling to grow straight. You should see a lot of growth on the leaf size and new leaves forming as well as height growth. On another note, that soil looks pretty wet mate. Are you watering around the seedling only, or all of the soil? Check out my current diaries and you will get an idea of how much I water as you will see the wet circle on the soil? There are a lot of hurdles to jump when growing as I found out from my last grow which was my first. I spent the majority of it confused or stressed 😂 Get the water, light and environment right and you will be off to a good start. Try and focus on getting those areas right first.