Squad 4 has a specific ability. When it comes to healing, only Squad 4 can have less concentration on healing. Meaning that they can heal someone even with distractions.
Soldiers: Can still heal with light distractions like with talking going on or while talking
Officers: Can still heal with some distractions like even doing something with one hand while still healing with the other
Lieutenants: Can still heal with major distractions like using their feet to heal
Captains: Can still heal with total complete distractions like healing while running.

They are also the only squad to be able to use healing Kido without training.