It usually takes maximum of 6 months. So if the visa officer put that interview requirement note in December, you will recieve an email from IRCC in May 2025 for an interivew date in June.
They send the email exactly 30 days before the interivew date.
In the meantime, if you have any documents, evidence of trip, or any other materials which you can share with IRCC which will provide more visual evidence that its a genuine relationship - pls send it asap and in the explanation letter - ask them to schedule the interivew asap cuz of current war sitaution. Interivews are usually done onlind over Zoom, specially in the current situation. IRCC officers from London office conduct the interivew and your spouse will be invited to Visa application center in pakistan - to sit infront of computer and respond to their questions.