On a T6.1 I understand the rear shelf is an inch or two shorter, prior to this there was only about 6 inches of leg room for the passenger directly behind the seat, theres now a little bit more room!
If the passenger behind the seat is in a booster seat it works ok with the shelf in place. People with longer legs also have the option of putting legs to either side or both one side of the 5th seat.
When ours was being used frequently we left the shelf at home & slid the bench back a foot. You've then got an excellent practical 5 seater & still have a huge boot. As Bellcrew said, put the 5th seat on the rails nearest the sink & the passenger in that one then has a great view out the front screen & has loads of extra legroom between the front seats.