My observation is that if I do this in the main note body, it isn’t a problem. The focused paragraph still gets saved wherever I stop and switch. So I naturally expect this to apply to properties. I suppose the app has a chance to save everything when user switches app. I haven’t observed data loss on main body for this reason, and it’s specific to the property.
If property is somehow special on that it has to save after the editing finishes, it might be better to make it less like note body, but use some different UI, e.g. a modal popup or something indicating the value is not yet in the file and you switch at your own risk of losing anything you put there.