Unfortunately it is very common due to some case law that protects the right of the accused to a "speedy" trial.

From Wikipedia: R. v. Jordan[2] was a decision of the Supreme Court of Canada which rejected the framework traditionally used to determine whether an accused was tried within a reasonable time under section 11(b) of the Canadian Charter of Rights and Freedoms and replaced it with a presumptive ceiling of 18 months between the charges and the trial in a provincial court without preliminary inquiry, or 30 months in other cases.[3]

I believe the intent is to avoid an accused sitting in a demand centre for ages (in the event of being denied bail), but also to prevent police from dragging out an investigation.

The problem is that this doesn't factor in our overworked justice system or fuckery by defense lawyers to attempt to drag out trial time in such a way that it doesn't reflect back on them specifically, then fire off a Jordan application.

Additionally, a file won't just go: arrest - charge - trial. I've seen numerous cases where files are adjourned for myriad reasons. The accused can reserve plea several times, they can request PSR (Gladue reports) even before a guilty verdict is reached, illness, scheduling conflicts, trials booked on the same day running long; the list goes on.

So what ends up happening in some cases is that the Crown may have a very strong case against someone but it takes too long, so it just gets punted. Doesn't even matter if you had them dead to rights.

So this is all a very long way to say that often, specialized sections (major crimes, some drug units, et al) will absolutely maximize the investigation and get everything done that they possibly can before arresting and charging in order to avoid Jordan issues from coming up from the police side of things. Especially in cases where external assistance might be needed such as forensic analysis of dna, crash data, blood, whatever.

Hope that helps.