Nvidia hardware accelerated encode for H264

My previous post was kindly answered by RjL190365 and his reply - marked as correct answer - was:

I am very sorry to tell you this, but only progressive scan video is supported for hardware encoding. Interlaced video MUST be encoded using software only.

I am not sure if this reply is for all computers or specific to my computer.  Please clarify this for me.  Thanks

My previous post was:
I have the following custom built setup for my editing with Premiere Pro:

CPU: i7-7700 @ 3.6G (Kaby Lake technology)

Windows 10 pro 64bit - using latest premiere pro cc update.

RAM: 32gb

GPU: Nvidia GTX 1060 - 6GB - with latest Display Driver 446.14 - clean installation.

Could someone please explain why these 2 sequence settings below produce different results regarding h264 export using media encoder? -

1. DNX 1080p (progressive) Hardware export OK (defaults to this).

2. DNX 1080i (upper field first) Software export only with the comment :" Your current hardware does not support hardware acceleration for the current settings."