Right?! I've done sensual massage, and three fingers off the bat only works if the guy is so loose that shit falls out when he stands up. LMAO Maybe Uke-san was not as "uninitiated" as we were lead to believe. LOL
Maybe the oil had a topical anesthetic like lidocaine in it. He wouldn't have felt the initial touch or sting and would only have noticed the internal sensation and pressure once the fingers were already inside. That said, any area where the oil was spread would also be numb, like his penis and eventually his anal cavity and prostate. Which would defeat the purpose. So, maybe not.
Three fingers suddenly slipping into the hole of an uninitiated man? That's not going to happen, believe me! :D