I agree that the NSFW-ness of a post is subjective - however, it needn't be something that results in confusion, flagging for NSFW is of no value without actually explaining that to be the cause.
In this case the images aren't even real wounds, they are known imitation injuries - how many jobs would be concerned with us looking at makeup? or even real wounds anyway!?
Yeah I wouldn't flag it. Yet when in doubt I use NSFW because of the flag happy few on the platform. Some of them have power.
Though it would be nice to know WHY it was actually flagged.