Banding on 32bit float, viewport and exports

So I have been trying to get my head around colour management for a long time and have read up on it quite a bit. I understand bit depth, profiles, gamma curves. I have a good monitor (Benq pd2700u) and have calibrated it.

I had noticed a little banding on gradients in After Effects and thought this is usual for 8bit, maybe my monitor wasn't quite up to scratch. But I thought I'd try a little experiment and so made the same gradient in Blender and what do you know it had no banding. So I tried creating a 32 bit float project in after efffects with a gradient - exported it to exr and opened it in blender - it has banding. I've attached a screen shot and AE file. Could someone please help me to understand what is going on here.