On Wordpress 4.9.8 and Civi 5.4.0.
It shows multiple values as long as you do not select all of the options. If you select them all, then it reverts back to just one (petitioning in this case) for some reason. Exporting data only shows the one value as well.
I tried to reproduce on a demo but it was on 5.0 version. Is this a bug?