It's never possible to know what (or whether
) a stude is thinking so it's useful when they go through their checks out loud or, for example, say what they are thinking when flying the approach (i.e. speed's good, angle's good, line-up's good - or something like that). It can help the FI in many phases of flight but it needs to be controlled and concise or else it can get in the way of monitoring the R/T to build a picture of where other people are. Also, it can add to the stude's workload so FIs wouldn't normally ask someone to do it.
HFD