Well it's hard to predict IRCC next move then.
I have no ideas why the background check takes different time between you and your wife. Maybe again I say maybe as it's just a spiculation. In the immigration process one of you was the main applicant or did more travels abroad than the other or shares a full name with many individuals in IRCC database so this requires for example fingerprint request to clear the case, which applies to you and not your wife as she did not receive a Fingerprint request if I'm right ? So maybe that's why her BG was completed as things went faster for her without FP request.
Again we cannot accurately and clearly know how things are run by IRCC.
In conclusion, the government is the same in any country. Where the bureaucracy reigns. Again, I'm just TWO blocks away from a processing office. I can see the Parking lot, people arriving between 8 to 9 (They start at 8 am), and at 4:05 pm, the parking lot is EMPTY. I understand that is their job, but IRCC should come with some incentives, like paying extra hours and maybe weekends for employees that are willing to get an extra bonus. I got told by one of them that they have a lot of pressure, IRCC has not hired any additional person in that office, and they haven't received any special instruction on rushing or having a daily quota. They are working as if nothing has happened. That person told me that they all know about the situation, but internally there is no rush.
That is why is really important to promote and tell people to sign the petition because it requires 500 to make a motion and 10,000 to get to Parliament. That last one is TOO far.... but at least the house of commons is a good step. IRCC should go back to the 12-month processing time.
Remember that in July, PR draws are back... so citizenship applications will spend more time in the queue. And that 2.1M people waiting for an answer, by August that number will be reaching 4M.
ANd yes, I agree... IRCC does not have a rule on how to process the cases. I've seen people that applied on Sept, that they already got their Oath Invitation.