They rooted the TV to study it. They're not saying you're in sudden danger of attackers rooting your TV and running commands over SSH. They're saying there's evidence that certain data is collected when you wouldn't want it to be, and there are any number of potential vulnerabilities that could provide hackers access, on top of LG potentially having access as well which you also probably wouldn't want.
They still run the audio recording manually through SSH and then claim that your TV is spying on your private conversations "silently".
Otherwise, they start a voice command service (clearly displayed on the screen) and then say your TV is recording on your conversation. Like duh, of course my TV starts recording voice when I use voice commands.
And of course you have to trust LG with their TV and (not) having access. That same logic applies to every different company.