@gaigous, Just to make sure, we are talking about the bespectacled midget, right?
I believe that if Seiya knows the midget well enough to knew about the latter's stress-relief habit, the former should also know well enough to not really bother him with unnecessary worry. Who knows, maybe Seiya already informed all the Super-Powered soldiers (he is one of the higher-ups after all) to prepares about the possibility of losing the element of surprise, and deliberately left the midget in the dark.
Plus, even with other choices available, honestly, having the means for non-returners to be able to at least stand up against the Returners is definitely a good idea.