I'd think all the wall sections are made the same. If the particular trailer model has a ladder for an option, then I'd think it would still have the backer inside the wall even if a ladder was not installed at the factory. Other wise the production line would have to in effect make 2 different walls for the same model floorplan. It's far easier to build the same wall whether you're going to hang a ladder on it or not. For that reason, if a ladder was originally available as a standard or option, I'd suspect a wall schematic will show where the reinforcing backers are installed for an 'after the thought' ladder.
FAA A&P mechanic, ex-RV dealer parts dept
Retired B-52 Gunner/Flight Examiner, B-52 Crew Chief
2016 Jayco Eagle HT 29.5 FBDS w/ 15,000 BTU AC, 50 amp service, upgraded counter top, thermal pane windows, elec. stab jacks, outside grill, backup camera and MORryde pin box.
2011 GMC 2500HD DURAMAX/ ALLISON