Normally would not caulk this area with the following exception. If you use the "shower" to either wash animals or do any activity down near the overlap, I would consider clear caulking. In TT's the design seems to be to let air flow between the shower and walls. When I asked a mechanic about this he suggested that sealing the area would produce mold.
2013 Chevy Express Van 1500 with 2500 rear end
2017 Jayco 23MRB: 26' total and Glacier Package
Married 43 years. Aki the "mutt," 12 years old "Excited to learn new things everyday and humbled by those who offer to help."