Well, after trying dozens of times over several months I tried using .mpeg (not .mpg) as the extension and it triggered something.
I am suddenly creating interlaced files! Makes zero sense. Just for the heck of it I tried the previous .mpg and it ALSO created interlaced material. Good grief.
I just used Avidemux 2.7.8 which has NEVER been suggested for interlaced and NEVER created an interlaced mpeg2 for me...
Well, I just used .mpeg as my extension and the darn thing is making an interlaced file.
And now...neither will produce an interlaced mpegs.
But...I have found AVANTI.
It seems to be making me very nice quality interlaced mpeg-2 files with little effort.
Sure, I might be late to AVANTI, but mpeg-2 is a mature format, being a little dated matters not, methinks.
Of course I can barely scratch the surface of the GUI, but all I need is a decent encoder.