I will let the engineer working the case help you. Regarding ifIndex and ifStackStatus, these are the most commonly used methods for indicating a logical interface's place in the interface stack. If a logical interface goes down, you will want to know whether, for instance, it is down because its physical interface is down. Also, in the case of vlans, you want some intelligence to show vlan device and port membership. Since Spectrum isn't looking for the TIMETRA-SAP-MIB when it's mapping out vlans, you won't have those associations between ports, devices and vlans.
Scott