An import or transcode of any material that does not match the project frame rate and raster type (progressive/interlace) will create media that is now that project type. For example, 1080i/59.94 material in a 23.976p project will become 23.976p material via motion adapters and the timecode becomes 23.976, losing the original 30NDF or 30DF timecode of the source. For some workflows, that is fine, for others it may not be. If you do need to go back to camera originals in an offline/online workflow then give my bog a read on how one can do that:
https://24p.com/wordpress/?p=22
I am assuming you are seeing the motion adapter because you are in a 720p/25 project and you now have the ability to change the motion adapter to 100% creating a slomo. If you were in a 720p/50, the file would already be at the proper rate and no motion adapter applied.
So depending on what you want to end up with, you can start in a 720p/50 project, transcode there, then open that bin in your 720p/25 project and you will now have the motion adapter available at your target codec choice.
Michael