The former SeaFrance pair still appear to have the gangway at the rear. They date back to the days when SeaFrance still took foot passengers. Calais Seaways served the route in the same era, albeit for P&O, but has been through so many transfers since it is possible the necessary fixtures are no longer present.
The Dover - Dunkerque ships (Delft, Dover and Dunkerque seaways) were never designed for many passengers let alone foot passengers they didn't have any any rear or side foot passenger ramps fitted when they entered service for Norfolk Line as freight only ships
The Dover - Calais ships are actually all equipt with foot passenger access
The Calais Seaways always had foot passenger access from when it was built and operated by Sally Line (Ramsgate) and when it passed multiple hands via P&O it ended up with DFDS as very much a specialist Dover - Calais ferry
The other two ship were built as the SeaFrance Rodin and Berlioz both on the same design (4 years apart)
They took foot passengers and still could and now running around as the Cote de Dunes and Cote des Flanders
Sadly DFDS don't see it as a profitable venture, extra costs like running a number of buses, staffing check in/ticket selling offices in terminals, and actually reducing capacity of the number of profitable lorries/vehicles carriable because the ships run on a certain staffing level to safely supervise an evacuation of upto a limit well below the actual capacity of the ship to reduce costs during quieter times.