I start my tomato seeds a smidge earlier than I actually should. I like to pot them up into 4 inch pots so they have a little more time inside to grow.
My tomatoes also tend to grow a bit taller than I’d like because they are always crowded into my limited seed starting space. Also, I think they would prefer a cooler temperature than we keep the house. Potting them up gives me the chance to plant them deeper so they can grow more roots.
If you look at a tomato stem (especially one growing a bit sideways), you can see little bumps. Each bump has the potential to become a root if it touches soil.
I plant my seedlings at the bottom of the pot, and then fill in with potting mix and water well. The plant can then start filling that whole space with roots, giving it more of a head start. I stake some of the tall ones to keep them from flopping over and getting tangled with each other.
When it’s time to plant them in the garden (hopefully late April) they can be planted deep again in the garden for even better rooting.