It seems like readOnly: false is the default mode (readOnly: true says, “nothing interesting for the program to run here”), so a screen could be looking for correct info from every component unless you tell it not to.
I, too have noticed that the order of placement for Note and Math Input components, in particular, can affect whether or not you get a check. The component elements seem to be interacting more like functional programming which works more linearly, I guess.