The reason there isn't any caulking there is because during transit the tub flexes due to the trailer frame flexing, etc. The caulking would just crack and be useless. Jayco, like most RV manufacturers have designed their tub walls to lay over top of the tub, so that no caulking is needed.
2010 Jayco JayFeather 213 EXP
2016 Ford F-150, 4x4, 3.5L ECOBOOST, MaxTow, Supercrew, 6.5FT, 3.55 axle