Sorry for the confusing title. If your player character is sitting inside a vehicle and gives instructions or otherwise says anything, the 1st portion of the sentence is played outside the vehicle. For instance, I command my squad to get in the vehicle with: "All, get in that vehicle". The "all" sounds like it's being played from a point outside the vehicle, the "get in that vehicle" is played inside as expected.

If the sentence is a single word command, then it's played outside: "Dismount" is played outside. However "Two, dismount", "two" played outside, "dismount" played inside. So it's not word specific, just whether the word is at the first part of the stitched together sentences