The closest related option is "not as described" or something like that.
Even if you contact support chat that is the only option available to the advisers too.
So it's actually impossible to report something as counterfeit.
I always imagine some C-level exec looking at the stats and congratulating themselves on having no counterfeit items reported. Well done Bob! We did it again.
How do you think they got to be that big?
More recently, I was lied to repeatedly by agents who told me that they were going to do something, or had done something already. I had to contact support many times, and the issue was only fixed after I was able to escalate to the executive support team, who confirmed I had been lied to repeatedly, and who were able to fix the problem.