One is a vacuum line and the other is a coolant line. You can get away with the coolant line not being connected as it just runs coolant through the shell to warm the TB. Not really needed if you live in a warm climate. Its pretty juch a must if you deal with cooler weather cause the TB can freeze up and stick. COULD.
The vacuum line goes to a sensor. Air is fed to the sensor via 2 vacuum routes so missing one is "probably" not much of an issue since the other line (not shown in the pics) runs into the plenum behind the TB. In all honesty, if it isnt throwing CELs, I wouldnt bother. The less lines snaking all over the place, the better in my book.
Gary Noonan
'01 S/C VX / '18 Forester XT