If you have an animation with the duration of 2 seconds at 30 fps and you change the framerate to 60 fps, Blender will keep the number of frames in the animation, changing only the playback rate. Meaning your animation that used to be 2 seconds is now 1 second long.
This makes sense in a straight forward way, but it’s not ‘smart’ in an animation workflow way of thinking.
Most other animation softwares (such as After Effects, 3ds Max, Maya, etc) preserve the animation timing when changing the frame rate. So if you have a 2 seconds animation at 30 fps and change the framerate to 60 fps, the animation will still be 2 seconds long, it just now will have twice as many frames.
I’m not mentioning other softwares to make a “that’s the standard” type of argument. I’m not saying that’s how it should be done just because other softwares do it. My argument is that most other softwares do it this way because it’s more useful most of the time.
From an animator’s point of view, this is what we want 99% of the times we change the framerate. If I animate a scene at 24 fps and then realize I need it at 30 fps, I’ll almost always want to preserve the timing of the animation I have already created.
In Blender we have to use the “time remap” function or scale all the keyframes in the animation to match the new frame rate, but that’s a messy extra step.
So in my opinion there should at least be the option to preserve timing when changing frame rate. In other words, the option to have Blender automatically recalculate the scaling of all the keyframes in the animation to keep the timing intact when changing the frame rate, like all reasonable animation softwares do.