"Interpret footage" not available for stitched clips?

Adobe Media Encoder is unable to recognize, that my AVCHD footage is shot in 25p and not 50i. (from Canon c100) It continually misinterprets my footage.

To fix that, I want to tell AME, that my footage is indeed progressive. You do this by choosing "interpret footage".

No problem, as long as I handle the clips individually. Then I can interpret and transcode to prores with no issues. So far, so good.

But if I want to use the "stitch clips together" feature, then I can't press "Interpret footage". The option is greyed out when I select the stitched clip.

Is there a workaround for this? So i can get both the stitched clip AND the correct interpretation?

A related question:

Does it even matter, that AME thinks my footage is interlaced? I assume it would affect the way the program transcodes to a progressive output? Does this interpretation affect/decrease the quality of the (progressive) output?

Kind regards and thanks in advance.