space bar completion mode on iPhone / iOS not working

I recently switched from Android to iPhone because third party keyboards (namely SwiftKey) are now available. However, on iPhone when I click the space bar to insert the highlighted word in the centre of the predictive space bar, it doesn't work as it did in Android. I must click the actual word in the predictive text bar. For example, in Android, you could just keep tapping the space bar and the highlighted word would be entered. I can't find the same setting in the iOS version. Is this a limitation or am I missing something?