There are pedophiles quoting that an explicit clear consent to sex is not always necessary, because they are able to "see" that it "wants" to have sex. Sometimes even an explicit "No" of the child may be caused not by the real wish of the child not to have sex, but by the sexual repression of the child. That means, the child wants to have sex, but his sex-negative education leads to an official "no".
Considering the current sex education of children, it really seems probable that a child which really wants to have sex says "no", at least much more probable than the reverse. If such a pedophile correctly detects the situation, it may be really not very harmful for the child.
But, nonetheless, I'm strongly against such contacts with only a guessed consent of the child. It is a violation of his fundamental human right of sexual self-determination. It is necessary to accept if it doesn't consent explicitely. A probability that it will later regret that it has not consented is not an argument.
The question of a certain or uncertain consent of the child has to be distinguished from the question of verbal or nonverbal consent. A nonverbal consent or dissent may be much more clear compared with the verbal.