It's called a Farmer John style and they're not meant to be worn separately.
Most often you'll find them in 5mm & 7mm only for scuba; and not in mixed matched thicknesses. They also usually don't come with an attached hood. If they do, it's usually front zip jacket that zips up to the chin of your hood.
Freediving styles will have 3mm varieties and they'll have the exact style in your video predominantly; or Mako's pictures.
The only difference between Scuba & Freediving suits are the neoprene material (Closed-Cell VS Open Cell). Freediving suits are much more flexible, usually skin-in, and delicate on the body lining (you have to worry about tearing it with a finger nail).
You can technically wear the bottom and a hooded vest over top, that way you have bare arms. Wearing the bottom solely will parachute you in any sort of current or swimming, so it isn't advised. You can get minimum insulation properties from wearing the bottom alone because of the problem I just stated. In some conditions you can get away with it though.