Although they have the same name and content, the two are different products. If you want to login through Telus, you will need to set up an account through the Telus interface. You can, of course continue as you are doing through your internet connected TV.
The reason? Likely privacy concerns preventing either company having access to credentials stored by the other.
I was able to successfully use the Netflix app on my Telus box. I had signed up for Netflix before it was an option through Telus. I had to login with Netflix credentials to get it to work.