Thanks !!
Upon further testing it seems like when using the harmony remote on the virtual keyboard, it is is currently sending the code to click on 'search' after you have typed what you wanted to search, but not what corresponds to 'i want to type that character selected on screen'
At least when mapping the central ok button on the shield remote to enter/return on the full keyboard layout in the flirc UI.
When you type a few characters with the shield remote or the Android TV phone app, and the click OK on the remote, it sends that search correctly.
Some apps such as Kodi don't have the issue, presumably because they have implemented their own keyboard and it responds well to the 'ok' button press