Why was this man not charged with this offence that it seems he has committed?

Question

I was reading this article, Man jailed after sending photos of his genitals to undercover police officer.

This article states:

Malcolm Blount, 55, was caught by police after he emailed three pictures of his genitals to an officer posing as the 12-year-old girl.

He was arrested for a few offenses but NOT Causing a child to watch a sexual act (Section 12 of the Sexual Offenses Act 2003). If you look at the Sexual Offences Definitive Guideline

One would think category 3 would apply. Perhaps I am not clear on what "Sexual activity" in the legal sense means. Would this boil down to the genital being erect or flaccid? There has been a recent provision to Section 67 of the serious crime Act (2015), called sexual communications with a child (2017).

which he would have been charged with, but the offense was committed in 2016.

In this instance, what constitutes a bare minimum of sexual activity?

Answer 1

There was no actual child who was caused to view the material, so there was no offense under that provision.

By contrast, inciting a child under 13 to engage in sexual activity is an inchoate offense, so it is not necessary for any harm to an actual victim to have occurred. Note that the relevant section of the Sexual Offenses Act 2003 concerns "causing or inciting," and that the charge was "inciting." The section concerning watching a sexual act, by contrast, only inludes "causing."