Yes pump can leak. #1 reason it leaks, is due to air vent at bottom of pump getting clogged. Than as motor spins, it creates a vacuum in motor housing and sucks fluid from pump. The seal in the back of pump is not a pressure seal. This seal in back of pump, can also leak/weep on it's own. Seal just leaking on it's own is not all that common, but does happen. Toyota put a canal from seal to daylight (bottom of pump). I presume this canal is to allow minor seepage to just drip out, rather than pool and get into motor damaging it.