After everything is said there is one question and only one question....how did the images get on his computer if he didn’t save them?
It’s a technicality of how web browsers work. Web browsers generally save off everything that was viewed into a file, although some can be put into a mode where this data only goes into volatile memory and never a file. This is for the convenience of the browser in rendering an image upon the screen. Web browsers usually have default settings where these saved files are kept for a finite time if not forever, for the sake of speed should the associated web page be visited in the future. (The local copy is rendered, rather than a freshly downloaded copy.) The browser does not know from porn. It could be the Vatican museum for all it knows.
When you see a picture on a web browser (on your computer), it’s been downloaded to your computer.
You’ve “downloaded” many pictures that you’ve “never downloaded” ... :-)