IMO, a preliminary hearing IS a test drive of the strength of the case the Crown is presenting, so the Crown referring to it as such is appropriate. This is not like the Bosma case where the evidence seems to be so strong that the Crown can be uber-confident in going with direct indictment (no test drive there). Not every case is a slam dunk and especially one where bodies have not been recovered. At this point, the Crown is going forward with forensics combined with circumstantial, so it's not surprising the prelim will be a test drive
As for wanting to "see where we're at" ... the judge will weigh the strength of their case, and if they aren't "at" where they should be, the judge won't send the case on to trial (finit .. no "tweaking" is required or gets to be done to fine-tune after the fact) and the accused can be discharged.
ETA: Kindly, sympathetic and elderly does not equate to stupidity (I hope). As a nice person but also a learned judge, perhaps he won't appear such after he's heard all the evidence, LOL.