Slow Motion Video Setting

What is the point to having slow motion setting if the original video won't play as slow as the original? I film birds in slow motion and wanted to make a movie of two of my slow motion sequences. I also wanted to put it to music. But once the footage is uploaded to iMovie, or even Youtube the video seems to play faster than a movie that was not filmed in slow motion. And even if you adjust the speed it's still not the same as the original. So why did you people invent this option on the phone if you can't use the footage in any capacity other than to take up storage space on your phone? I have always been a devout Apple product user, because of the software always being so user friendly. But over time with every creative project you keep making updates, changes, whatever. And now something that should be simple now has to be so complicated. I can't even play old imovie projects because you updated the app. So I lost 80% of what I had. Stop fixing crap that isn't broken!!! P.S. This form on here asking me what device this is about..... It's about my phone, my macbook, ios, imovie - ALL OF IT. I only clicked on one because you won't let me click on all. Which is stupid.