Its hard to really tell! You also have to factor in the distortion in the video! Usuallybwith these shots they need wide angle lenses so what u will probably see is a distorted perspective/view! I also have this gripe of the CLA maybe being too small but since im just about 5'6, and i think the tallest of my friends is just 5'11, it makes me quite hopeful about seating comfort/conditions when I have passengers!
I'm not overly worried about the back seat, if I have adult passengers in the back it will be rare and my kids are small enough, my main concern is the front seat. I'm 6'4" and I'm willing to bet Wolfgang is a smidge shorter and he looked a bit cramped.
I'm thinking someone 6'1"+ in the back can be somewhat comfortably seated if the front-seat is kinda/sorta far up allowing for leg/thigh room & slouching. And someone 6'1"+ can be very comfortable in the front if not having to contend w/ positioning the seat for a rear passenger behind them.
I've seen 6'5" drivers comfortably get in/out (and drive) many high-end high-performance sports-cars (not sports-coupes or GTs), based on some seat adjustment/toggling.
AMG Boost had a great suggestion that we sticky a thread that contains posts/pictures from owners of their brand new CLA's... So, without further delay, here it is! Post pictures of your brand new CLA in this thread.