Right, I guess that has more to do with how you are trying to get their body to react, in which direction you want the center to move.
But in the interest of keeping yourself safe, even a weak strike, if thrown without some knowledge of correct striking form can lead to damage in the hand and wrist.
For the weak strike, if you hold to the traditional closed fist strike with the knuckles, on a hard target, yes.
I don't know what types of strikes are outlined originally in Aikido, but for this discussion an open hand strike for example to or toward a soft can be very deceptive and effective even if it is a weak strike.
If you really look at it a effective strike to a soft target really doesn't involve allot of skill, and doesn't result injury. Unlike the traditional closed fist hand strike to a hard target improperly used results in injury. A open hand strike is more deceptive and more likely to get a reaction that will open or move the center. If you use a traditional close fist the reaction will be highly defensive because it is so recognizable, thus, the center is less likely to be accessible or moved. Most likely the defensive body reaction to an on coming typical close fist leads to protecting the center from moving in a bad way. We are talking about a single static hit, and not a wild barrage of flying fists traveling like a speeding freight train?