How does speed/duration work?

Hey, team - just a quick question about the speed/duration settings and how they affect clips.

I have a sequence that is 25fps. There is a bunch of footage (mostly shot on drone) that is imported at 50fps. Now the way I normally work is I go through and interpret that footage normally as 25fps so it plays back as intended. But I'm working with a few other editors on the same project... And they always leave the footage at 50fps, pop it into a 25fps timeline and then use speed/duration to reduce it down to half speed. At this point there are a bunch of sequences already put together so I don't want to go through and change everything that is 50fps down to 25fps because it'll change all the in out points the other editors have done.

How does Premiere interpret a 50fps clip with a 50% speed/duration change inside a 25fps sequence. Does it bring it in, convert it to 25fps. Then when you change its speed by 50% it's reducing a 25fps clip down to 12.5fps? Or is it recognising there are 50 frames of data there and reducing the original clip to 25fps? I guess my main concern is changing it's speed with speed/duration going to make it choppy vs changing the interpretation of the original clips frame rate?

Sorry if that sounds more confusing than it needs to.