My company does, and I find it pretty easy to weed out the LLM candidates either way. "You used a heap here, can you explain why?", "why did you name your variable [something unrelated to the question but relevant to the underlying concept]?" will send them stumbling or "just a sec, I need to think about it". That's obviously not how it works, if you're actually writing the code you'll have thought about it before, you won't just throw in a heap "just because". It's also not super hard to figure out when someone is just reading something off of the screen, especially when they clearly have a second monitor, or a phone, or a tablet nearby, but even on the same screen you can see their eyes dart back and forth.
The bigger problem for us is the online assessments that they give out as a replacement for the phone screen nowadays. They clearly can't detect LLM use, even though to me as a human it seems quite blatant - things like extensive use of comments explaining the code, which should throw up a red flag on an assessment where the only thing that matters is passing the test cases. So we get a lot of candidates at on-sites that would have never made it past the traditional phone screen.
As an aside I initially only ask "LeetCode easy"-type questions. Stuff you would encounter in your day to day. You get to choose your favorite language. There's at least 3-5 solutions for each of the problems I give, they're really not meant to be trick questions. Any dev should be able to code these in 5 minutes without even googling, let alone need ChatGPT. I almost think some people use ChatGPT out of habit more than anything else and it trips them up more than if they had taken a minute to think about it and do it themselves.