If it's not automated, it could easily be some sort of pre-defined script. I don't get many anymore, but I've definitely had mysterious text messages from different numbers supposedly across the country that were nearly identical. Usually it was "hey is this [random name], where were you last night?" I assume this was meant to draw me into some sort of dialogue. It happened enough that I can't really believe it was just a misdial.

From what I understand, initial messages don't come from the slaves; instead, you get connected to one if you reply. So the english skills might shift drastically between the first and second message.

They started off targeting Chinese speakers (Mainland China, Taiwan, HK, Malaysia, Singapore) but expanded into English and Thai over the past few years.

I'm guessing that they're mostly targeting the richer Asian countries, including China (which is on average is poorer than the West, but in the aggregate has comparable spending power as North America).

A relative of mine got scammed for tens of thousands of dollars exactly this way. They are college educated, COO of the company they founded in the US, and thought they were just making a new friend over several months after receiving a message that was addressed to them by error.

"Many of the victims are well-educated, sometimes coming from professional jobs or with graduate or even post-graduate degrees, computer-literate and multi-lingual." (from the report)