Lots of apples and oranges here! There are 3 way RV fridges, 12V, 120VAC, and Propane. These are the oldest. The 12V function was discontinued because it would drain a battery. Ours, for instance, is a 2-Way, 120VAC and Propane. Propane works great. However, lately some have become "scared" of propane, and go through all kinds of hoops to not run the propane, especially on the road. (which is what it is designed for!). These have all been absorption fridges, which heat ammonia to boiling. Now, because of the propane fears, a newer type of fridge is being offered that is all electric, i.e. 120VAC and 12VDC. There are also those who favor using a regular, home-style residential refrigerator on a big bank of batteries with an inverter! Supposedly the newer 12V ones use less current, but still recommend a second battery.
To give away my age, our first refrigerator when I was a kid was a Servel. Natural gas, absorption, in our kitchen. They've been in use for years!
Now to the question that started all of this:
Yes, your 12V+ on the 7-pin does connect your Titan 12V system to the trailer, when the engine is running. There is a relay that cuts it off in the truck, to keep camper usage from draining the battery. Be advised, however, that due to wire gauge and length, current is limited. Even at highway speeds, the ability of the truck to recharge the trailer battery (ies) is/are limited.