Not sure which "previous" Pro Ceed are you talking about as Cee'd is noticeably different than its Pro cousin. Especially if you refer to MK1 models...
The Mk 1 Ceed and Proceed have the exact same bodies from the "B" pillar forwards as do the later Mk 1's with the "Tiger" nose, the "Tiger" nose did arrive later on the Proceed. Because the front door on the Proceed is longer the "B" pillar is further back. Behind the "B" pillar the Proceed is different, it has to be, its a couple of doors short.
The interiors of the Ceed and Proceed are identical with just a few spec diofferences.
Like I said, the Proceed is just a Ceed with a couple of doors missing.
Its a matter of economics, volume manufacturers keep as many parts standard as possible between as many models as they can.
Ford lost a fortune on the Puma, looked great but every panel was unique as was part of the interior. Have you spotted how they have not repeated the excercise.