I took the backend test expecting programming and SQL, but it was hard-core DevOps and SysAdmin. Had nothing to do with programming a backend system. I know a little about working with command line and admin, but using tools to orchestrate 100 servers isn't something I know about.
My impression is that it's built with a very high failure rate built-in, targeting people who have a very specific and easy-hire background. I'm not really sure if someone of this talent level would really need Triplebyte.
I'd guess a very large portion of that 40% just end up getting a job the old fashioned way.
Edit: I admit didn't pass the in person part and I have some issues with things I think were held against me when it was more confusion about what they were looking for, but overall I thought it was a great process and have recommended it to people.