Do you not mean LNAV, which is would be why you say
providing we have the raw data needle overlaid as back up.
?
May sound like egg sucking teaching but VNAV is for vertical. The needles that are available during an NPA are for "Lateral" guidance.
Some operators use VNAV/LNAV though but not NJE and its Excels. On the other hand, LNAV overlaid is accepted.