I believe Baldur may have been referring to the following statement that you made:

"I have lived smarter, and never been caught in 40 years of CL. So was really unable to answer those questions truely, because I had never been arrested."

This statement and, in particular the phrase "never been caught in 40 years of CL", could be interpreted as an admission that you have been involved in a pattern of illegal activity over the course of decades.

The reason that the survey authors asked participants to admit only to " ... sexual contacts with children that had come to the attention of the legal system" is to protect themselves as much as any forums where they have posted. The researchers don't want law enforcement breathing down their necks, attempting to investigate alleged unprosecuted offenses, any more than the operators of GirlChat do.