even if you decide to later install the trailer module, the pins 10 and 12 have NO influence on the operation of the module - the two signals are taken in and one "combined" signal comes out on the pin 3 of the module for the purpose of trailer foglight, which is NOT present NOR wired in US spec cars...

so, whether pins 10 and 12 are inside the plug or not - makes no functional difference in trailer module operation...