I'd say that's good growth! Same age as my little guys... I've got about 35 of them of different named mother trees... And although I've got a couple taller ones most of mine are on the smaller side maybe only 8" from soil line and I don't think any of mine have branched. When I kept them, I was looking for reddish tinges to the stems and leaves because I prefer the darker colored flowers, and not lankier growth or branching so that's how I culled them (sold or gave away most, but it's a crapshoot with seedlings so my best ones might have gotten away to some lucky person!)
Your look great! I hope they bloom for you soon!

Ditto what Disney said--they look great!

They're likely to bloom faster if you put them in the ground during the growing season, or even plunge the pots so their roots can get out into the earth.

Of the twenty seedlings I kept, only one bloomed before 3-years-old, and it was a beast. Also had an inflo on another same age that dropped all its buds before opening :(

Now I've discovered two that had what looked like false inflos but are actually budding at 3-1/2 yrs old so I'm excited! A couple of my friends who have my seedlings are reporting blooms, too.

Nearly all these earlier bloomers are in the ground for the season, and bare-rooted over winter.