A Raspberry query

I have a bed of raspberries which I believed to be half Autumn Bliss and half Polka (another autumn variety). It’s about 4 years old. The Autumn Bliss are fine - I cut the canes down to the ground each February and they fruit reasonably well. The Polka are supposed to be treated the same way so I have cut them back each February. But they just grow tall 6” canes, look lush and green but don’t fruit (except for the very occasional berry). I started to wonder if they might in fact be summer fruiting canes - so this year I didn’t cut down the Polka canes. They are now looking fantastically green and healthy and are getting flowers. Does this mean they are indeed not Polka but a mystery summer fruiting variety or could they still in fact be Polka? 

Thanks New Shoot. I wonder what they are then...still, as you say, if they fruit well (fingers crossed) I won’t mind, I’ll just know to treat them differently.