I'm new to the forum but wanted to share some information.
I'm a single guy who lives in SLC and use Tinder, Bumble, Match, and the arrangement site that ML was on.
Tinder is a pretty routine and normal dating site. I'd guess 90 percent of single people in their 20's are using Tinder. I vaguely recall seeing ML's profile on Tinder.
The arrangement site has several thousand women on it in Utah. I've seen screenshots of ML's profile on there but don't recall seeing her profile there. I've not seen any screen shots that AA was on the arrangement site. If he was, I think someone would have posted it somewhere.
I've read speculation about what ML meant about "online only." There are certainly a lot of women on the site who are looking for "online only" but that means they do not want to meet in person. Usually, online only means they will send texts and pictures, etc. I've not done anything like that (I can't keep up on my texts anyway!) but I get a sense its often pretty vanilla.
As for in person arrangements, these usually look a lot like normal dating but more direct. I've certainly met women from the arrangement site but everyone (including me) is very safety conscious. I've never heard of anyone meeting from the site at a park at 3 AM! Like regular dating, its more likely to first meet for coffee, lunch, drinks, or dinner. Also, its pretty obvious on a date when someone has texted a friend to say everything is OK. I'm pretty confident that women I have dated through the arrangement site have told their friends who I am -- for example, I have seen their friends visit my LinkedIn profile and have met some.
As I read the news, LE was able to connect him to the situation by seeing they were texting each other. That means they had each others real telephone numbers and weren't communicating over a dating site or using an anonymous phone app. She wouldn't have given her real telephone number unless she was comfortable. As others have said, he's hardly a rocket scientist and was working at the basic help desk level, likely setting up people's new computers. I'd guess she was making more than he was. He also was comfortable enough to give her his real telephone number.
I've seen his Meetup profile and seen some comments about his interests/lifestyle. I'd guess he is a member of Fetlife, which is definitely not Tinder, Bumble, Match, or the arrangement site. I'm not a member of that and haven't read anything to suggest she is.
I'm curious about his source of money though. A help desk tech like him doesn't make much and I don't know he'd get approved for a loan.