I know two people with same situation like you have but with a little bit difference.
One person who got passport request, and CHC London gave him visa even his medical just expire a week ago. He was given 45 days to land otherwise, re-medical and re-issue of visa.
I also know a person, who submitted his passport, but medical expires after submission. Then after two months, embassy ask him to do re-medical, submit it and when he submitted it, they stamp visa on it.
I think that may you also get the second sitution.
Although, there is no speicfic rule, and it all depends on the VO, but we can only learn from other's experience.
I hope that it will help.
Me and my brother also applied under 4131. My brother sent his full documents nearly 9 months ago but still Ecas is RBVO. We sent last week email to CHC London, and got reply, that there are nearly 475000 applications and so far, 185000 are un-decided. We were advised that may our process gone to two years or more.
I sent them again an email and asked from them that can they confirm me that either application is the part of un-touched applications or not. Waiting for their response. Lets see what happen next.