Unknown factors are more of a deterrent. If their power level is known, even if it is something massive, there's opportunities to prepare for it and try to find a response to it. If we have no idea what it is we might be up against besides those who intervene as necessary, however, it breeds hesitation because nobody knows what might come down on them if they cross a line.

[Mikumo makes the observation rather bluntly. It's something she's experienced with her own military dealings, that unwillingness to reveal the true extent of power until it's actively being used. The strategic route, in other words.]