If someone's name is in the viewers list, they can have paused the stream and left the page open, or have the chat popped out and closed the main window.
Just wanted to add to my rep comment.
I've been in the viewer list in a match in SEAL - but with my internet I can barely watch streams.. let alone have SC2 open aswell, the one occasion I was in the chat list - is as you said, because I had the chat popped out.. as I was in viewing other players games in SC2 and chatting in the chat. And neglected to close the chat when it was time for me to play. I didn't cheat in those games...
BUT, when I was asked about being in the chat - I responded straight away with "wtf?.. oh shit I had the chat popped out and totally forgot, I swear I wasn't cheating" - not, 'my gf was watching on my account..' firstly, why would you give someone your twitch log in details to watch you play?.. you can watch with out logging in.. then he said his GF was behind him watching the game on his screen.. so who actually was on his account watching the game?...
It's inconsistencies in his defence and the circumstantial evidence that makes it seem he is a hacker or a cheater.. I'll admint, there isn't anything that is conclusive. but it is very, very, very suss.
Even the smallest donations help keep sc2sea running! All donations go towards helping our site run including our monthly server hosting fees and sc2sea sponsored community tournaments we host. Find out more here.