Hi xerves,
In this case a force reinstall is the correct action. (I believe hovering over the force reinstall button will mention something about updating to the new build).
The reason for the wording is that new builds ( v5.3.6 b4 -> v5.3.6 b5 ) are not treated as new versions like and update from v5.3.6 to v5.3.7 would be. So what you are doing here is reinstalling the same version, but a newer "build" or package of that version. We do this to release improvements and bug fixes to the released version while we work on new features etc for the next version.
Hope this clears things up a little,
-Michael