Per the LJs, Sol has also gone out on administrative leave at least once, after shooting the telekinetic gamma who It does seem to be a consistent requirement after an agent kills a suspect, probably because every such shooting has to be investigated.
Considering the WTF terminates gammas with extreme prejudice on a regular basis, it means they're going to be below full stength as often as not. Mind you, while I'm not saying that familiarity breeds contempt, it does have some advantages -- in what other unit could you get away with breaking the UNSUB's neck with a lamp-cord....