We got our Wrangler Sahara 4xe 2 weeks ago and are pretty impressed with it.It actually looks like the rear seat bottom and back is carry over from the Gladiator. the JT has a very similar design seat from what i can tell.
We ordered weathertech mats and found that the back seat floor mat and the cargo liner mat did not fit. Looks like the leg room is 2-4 inches shorter than a standard Sahara. WeatherTech said I was the third person to call with this problem because of the back seat size - they haven't (as of today 4/19/21) gotten to a dealer and measured the 4xe dimension to create a new back seat floor mat and a cargo area liner.
The trick is that the battery is under the whole back seat - it looks like they made the back seat a few inches wider in the front and a few inches wider in the back. So I measured these spaces:
To measure leg room, I put the front seat all the way back and measured from the back of the front seat to the back seat cushion, which measured about 8". In the cargo area, I measured from the spot where the floor turns up sharply at the back of the rear seat, to the rubber gasket around the back door and got about 32 inches
If someone can send the measurements for a 2021 non-4xe wrangler, we'll know how the rear leg room changed.