A few, yes.
Anecdotally, on reddit - there are complaints by Eb3 unskilled filers who admit to using agencies - they are assigned to jobs that don't pay enough for where they live.
You'll see on Hacking, people who get GCs when they arrive but there is no job for them. Hacking is very suspicious but if you make yourself available for the job,
I don't think it's a scam.
Maybe just never naturalize and be happy with a GC.
There is a website that claims to show the employers who file for EB3 petitions. You can't sort by unskilled/agencies BUT you can sort by salaries. https://www.myvisajobs.com/reports/green-card/
My hunch is that salaries under 50k, 40k are EB3 unskilled positions.
Top industries are poultry and other food processing jobs.
There looks to be a high rate of approvals, so I'm sure the process completes and I'm also confident that "Wayne Farms" and "Catfish ..." recruit through agencies.
If one looks at where those factories are located and add a google search for "recruitment agencies", I'm sure you can figure out the name of the
agencies.
Back when M was active, he said that he thought it was a little known but (relatively) cheap way of getting a green card. Better than EB5 if you think about it - no conditions to be removed.