Hi - yup, you just get the average hr, the hr graph gives the live reading but I'd be the first to admit that it's hard to read when you are on the move. You can exit TE mode with a long press on the back button (bottom left hand side).
Not sure if it's available on the T6 - we're taking about a display function on the T3. Enabling TE mode just changes the main display from 'heart rate' to 'training effect'.