There are teenagers who look 11 and there are teens who look 21 in real life… It’s rare but it exists, most teens look like teens though.
One thing I liked about Discover University is they actually looked to see how teens and early 20 somethings dressed, so I could make YA sims look like they just graduated high school (for once). Most of the time they dress up sims of all ages in pretty grown up outfits, then again maybe I just prefer more youthful styles.
But for my sims game I want there to be a difference in looks for all the ages, it’s too late for sims 4 but I better see teens have their own height again in sims 5.