Not sure if it's the same, but I interviewed with TheoremOne last year and the first assessment they sent was essentially an asynchronous interview where you recorded yourself answering a bunch of questions. They were standard interview fare, and a couple engineering fundamentals. After that it moved to actual interviews.
My process was for management so SWE may be a bit different- I can't speak to what kind of in depth technical assessment they do for SWEs.

FWIW I ultimately declined an offer from them- while the pay was good (too good, danger pay), they basically do staffing for banking and finance clients, and asked for a bunch of details like a credit check and drug test as part of onboarding. The work didn't seem compelling and it seemed to suggest things about how people are treated that didn't jive with me. Just another "consulting" firm. 🙂

Lol, I was actually rejected after the first interview question, and I don’t really understand why I was rejected