Does getting braces improve the jawline?

I see a friend who got braces even though their teeth are fine.

We are not very close friends, and I don't contact him often.

I didn't ask in detail, but...

After getting braces, my jawline became incredibly slimmer.

It didn't originally stick out, but after doing it, it did.

My chin has become completely pointed, almost nonexistent.

Does getting braces make the jawline look slimmer?

My former coworker also said they were getting braces because of malocclusion.

After doing it, my underbite completely disappeared.

I'm worried that my niece's (female) jawline is somewhat developed now, and I wonder if it will become more prominent as she grows older.

My teeth are fine because of my jawline, but I shouldn't get braces, right?