Tee Emm, the point being questioned appears to be the awareness and realisation that something is not as required. Speaking up, challenging, and intervention are options of what to do after the ‘monitor’ has been triggered.
piratepete, you assume that all situations will be covered by an SOP or that a suitable SOP is self-evident and its purpose and limits are known by the monitor.
Your example of SPEED means what ? Look at the airspeed, an error from the required value, a limit exceedance, or a failure. A better SOP might include information in the callout; ‘ Vref + 15’, for use on the approach below 1000ft.
Consider a circling procedure where the PF has briefed a slightly higher than standard turn speed (+5) for turbulence and a small addition for the increased bank angle. Is the approach callout still valid – yes, but it is more for information than alerting and might only change between the two modes at 300ft. Where is this defined, who judges that, who calls it – and what if the flight requires that monitor to look out to assist judgement of the turn, which monitoring function is more important?
There are deficiencies in monitoring; it appears to work when things are routine and progressing reasonably normally, but if not, then monitoring can fail. This is a human failure which may depend on what they are being asked to do, but also not aided, or even confused by, poor SOPs and assumptions.