Hi,
The search results page works completely separated from the plugin – anything regarding the layout of the results page is out of the plugins control, only the theme can affect that. The only way to do this is by custom coding the theme to group the results in a post process.
Therefore the ordering can be a bit different on the live and the results page when the grouping is enabled, since that cannot be applied on the results page by the plugin, it is impossible to do.