It is possible his confession was disingenuous. Let's take a closer look.
He had previous sexual relationships with her and she had invited him up to visit her the time the incident took place. Without the article specifying the delay between the incident and the phone call it's reasonable to assume it took place relatively shortly thereafter.
So, we have a guy who has a friend with benefits who phones him a few days after having sex and says, "You raped me".
Now, we don't know what kind of relationship they had, sex-wise. Was it straight forward where one would call the other and say "come over and let's get it on" or was she the dominant one always setting the agenda? Was it more of a, "you are a bad boy" to which he'd reply, "Yes, you are right, Mistress" type of relationship?
In other words was he thinking it was all part of the "act" and he would say he was a bad boy, apologize, hoping she would invite him over for a make out session?
Let’s take a look at the conversation.
Victim: "You do realize that … it's rape."
Suspect: "Yeah, I do."
Victim: "Like in a number of different ways, because I didn't want to do it and because I was intoxicated and because I was afraid."
Suspect: "Yes I do. I know."
I’m not an expert on rape, however, from what I understand women do not usually phone the guy who raped them and have a level headed, non-emotional chat. From anything I’ve read or seen on TV rape has been portrayed as a traumatic event with the victim either filled with rage or terrified of the man who raped them.
From my understanding detectives take note of a person’s demeanor when questioning them. Perhaps they felt her “reaction” was not appropriate.
As I said I’m not familiar with rape victims so although the way she handled it seems peculiar to me perhaps it is “normal”.