While it's not "technically" underage rape, let's be honest it basically is. No normal person thinks it's acceptable for some in there 30s to have a relationship with a 16 year old.
The law is there to protect say an 18 year old in collage, where it's common for 16-18 year olds to be in the same classes, not for creepy 30+ year olds.
He's abusing the law, it's obviously not designed for a 30 plus year old to have a relationship with a 16 year old.