Well I called Jayco and explained twice it is the rear back cushion,
There response was yea that wood goes where you sit WTF?
A waist of time She told me they probably forgot to put it the other side that they are not perfect and said to bring it to the dealer and they would fix it WTF?
I have the 26 ft Redhawk 2017 and also had a wood plank in the dinette cushion. In mine the wood plank cushion was Jayco' CHEAP answer for climbing up into overhead bunk. In other words it's a step. Talk about cheap instead of adding a ladder. My unit has no sofa and I guess they just happen to have some wood planks left over so they just threw it in. I have since modified the dinette with two recliners to replace to replace the original dinette. We have a ladder for grand kids to climb in to the overhead instead of standing on the dinette cushion and possibly falling and get injured for which Jayco would share no blame.
The cushion with the plywood in it is used in their shorter M.H. where the dinette is directly behind the passenger seat. To recline the passenger seat you remove this cushion and the back is cut out so the seat will recline. The plywood in the cushion gives the cushion some stability since the back has the opening. Jayco just uses the same cushion in many units even tho its not needed in many.