Standard definition issue

I am trying to use Premiere Pro for SD.  Before you ask, I deal in obsolete formats and preservation, so I need to use SD.

I had some captured files in H264 mov from another system.  Files are 720x480, 29.97i, lower field first.  I am importing to Premiere to make an mpg file.

When I drag the file to create a timeline in the format of the clip, it tells me the sequence is 29.97p!  It will export the clip with the interlace removed!

Even if I force the timeline into 29.97i, it will simply change the 29.97p back to 29.97i but with artifacts from changing to progressive and back again!

When I take MXF SD files from my P2 cards it will create a sequence that is 29.97i just fine, so I know it's capable of interlaced SD.

Why is Premiere forcing all other SD files into 29.97p?  I even tried converting them in Handbrake making sure it preserved interlace and the result is the same.