There is such a thing as enthusiastic nonverbal consent-- it's pretty hard to mistake. I've never been saying, "always ask 100% of the time no matter what". I've been saying, "If you have any doubt in your mind, just ask." And accordingly, to place the line of doubt somewhere a little higher than "She let me into her house."
Well, that's exactly what I believe that the author of the book was saying, if one reads his text with a slightly different, more realistic, bias. He wrote the book exactly because many men, after having heard lectures from people like you, fail to notice and act upon even the most enthusiastic non-verbal consent.
You do, of course, realize the absurdity of your statement here, given this:
"Without a clear verbal confirmation of consent, or an explicit proactive action, you cannot know if your partner is participating willingly."
How does that work, exactly?