If you just want to experiement with it for say a couple of weeks, does it really matter that the commands from those few weeks disappear if you decide not to continue using it?
Presumably you already have a long history of commands from past years in the original format. And if your command line usage is similar to mine, then most of the commands you will use in the future will be covered by your existing history.
So if a few weeks of experimenting with atuin ends with you deciding not to use atuin, then probably you will be fine going back to the old history files that do not include those weeks of activity.