Polyanthus seedlings and very thin stems

Do Polyanthus seedling always have incredibly thin stems?

I ask because I have some seedlings that are a couple of months old - on average each has six leaves, the largest of which are about an inch in diameter.

The main stems though are incredibly thin where they enter the soil, particularly given the size of the leaves that each seedling has, resulting in the seedlings being very floppy - is this normal?

I've only just transferred them from their seed cells to individual pots.