From what I understand is that they will finish processing everyone else's application and then schedule all of them together for a Oath...so 2 family members may be all green pending oath while the 3rd may be going through extensive checks as part of security or criminality.
All logical estimates and rationale understandings conclude to a mind mush when it comes to IRCC. I would sarcastically mutter IRCC line - every case is different. Though today 19 months time reduction means nothing, as beyond that its non-routine, within 19 months routine. The very definition of routine vs non-routine itself is controversial lol. Anyways, to your point, have seen cases where ones BG is completed and LPP
not started, while spouse BG is in process. Sometimes they hault, sometimes they process separately, at granular level - discretion of case officer, or other mysterious opaque reasons of IRCC, beyond rationale or common understanding to noobs like me...
