The way the dual recording works makes this complicated, it's pulling frame by frame as if you were manually moving the slider from the joint controls, this uses a common time axis for synchronization and is oblivious to the local slow motion of the videos. That is, a given position in the bottom slider corresponds to a specific time, in a common reference frame where both time origins are aligned, slow motion has no impact on that.
Probably a work around for now would be to redefine one of the video nominal speed by going to menu Video > Configure video timing and forcing a different framerate in the bottom part of the window. There is a bug related to time display with this function that is only fixed in the development version but this should hopefully not prevent the work around from working.
To clarify, maybe, in the current synchronization approach, the output at 1.0 seconds should always show what happened at 1.0 seconds in each source video.
I understand there is a need to compare events with different durations "as if they had lasted the same duration", essentially normalizing on the duration of one to be able to compare the forms only. I'm still unsure what's the best approach for this. It has come up a few times but it would help to have a good pair of videos with the corresponding objective.