Okay, so check this out:

Orginal excitement:
https://www.youtube.com/watch?v=W9Pw1n8buLA&t=74s

Stopping for TMJ/jaw concerns:
https://www.youtube.com/watch?v=mfxWC8xeccQ

Her maxilla was trapping in her mandible and because the mandible expanded front&back (according to her)... it was hard to stay in class 1 dentition.  Her mandible was being pushed back.  Where do you think this pushing back goes?  The airway.  If it WIDENS then it's better for airway.  We need more WIDENING/FORWARD movement and less LENGTHENING/BACKWARD.  You all here know this, though.  This is not rocket surgery/brain science.  However, people want FAST and they want STRAIGHT.  To get real arch expansion with aligners it takes years... then the  front get addressed.  Everyone wants quick fix.  Little do they know, though it totally depends on the case.  There are a number of factors unaccounted for with this stuff.  I will say this, though...

Check out this interview from one of the BEST (if not the best)... Dr. John Graham:

http://www.elevateorthopodcast.com/episode21/
Listen from 23:00 - 28:00 (or to 29:00 for TMD)

He's not dissing 6 month smiles, and is airway focused.  However, I think it'd depend on how their airway is to begin.  3D.. check the condyles, the nasal cavity, the roots, teeth and AIRWAY.

The whole point is some of these people are pushing their mandible backwards... into their airway... and they don't even know it.  Do you think Smile Direct is monitoring this stuff?!?!  They SAY they don't.  When people realize the connection with anxiety/depression/high blood pressure/etc.  I heard, even, diabetes.  And I always wondered about that.  Apparently that's from getting anerobic = not enough oxygen supply.  All this stuff... and more!  It's all unfolding.  Can't wait to learn more.