Gotcha - the delay is in response to user input when using the menu system..
Unless you can find the same display running faster.. I would suggest that yes thats about it. the lil processor in the display unit is struggling painting the response screens in the setting menus, they use the cheapest ic they can for the job or it could be cheap slow memory chips that hold the bitmaps?? certainly not in the same class as an intel 17 etc..
Not something you should be doing when riding the bike or frequently (more than once for initial setup) so its deemed good enough..
EDIT - an afterthought, extra delays could be introduced by less than perfect connections between the controller box and display requiring repeated resending of info before a clean acknowledgement (if required?) is provided. so check wires/connections (talk about clutching straws....)
As long as settings changes you make take - all is good.