Definitely people can absorb enough RF to block WiFi.
I hit this in a hotel, back when I was doing steampunk conventions. Antique Teletype machines put into brass and glass cases, getting text messages over the Internet. (Early versions of this used Google Voice to read SMS; later versions used Twilio.) The hotel lobby had WiFi, but the function room we were in did not. I'd tested in advance, and was able to get a good WiFi connection with the room empty. But once it filled up with people, we couldn't get through. Had to run out to Fry's and buy a WiFi booster.
I hit this in a hotel, back when I was doing steampunk conventions. Antique Teletype machines put into brass and glass cases, getting text messages over the Internet. (Early versions of this used Google Voice to read SMS; later versions used Twilio.) The hotel lobby had WiFi, but the function room we were in did not. I'd tested in advance, and was able to get a good WiFi connection with the room empty. But once it filled up with people, we couldn't get through. Had to run out to Fry's and buy a WiFi booster.