The idea that the SCC needs evidence of what the trial courts are actually doing in order to define unreasonable delay is backward. It implies that most cases are dealt with without unreasonable delay, and the definition of reasonable delay needs to be expansive enough that it will be unusual to find unreasonable delay. 

However, the logic is the other way around. First, define unreasonable delay, and then look at the trial courts to find out how common unreasonable delay is.

I would note that the court first tackled unreasonable delay in R v Askov (my view is that they got it right the first time), and has been steadily relaxing the standard ever since. Askov set the permissible delay at 8 months; Jordan says 18-30 months, and still allows "exceptional circumstances" to stretch that out.