I completely understand what you are saying. A top-of-the-line dog with a really conscientious handler would use the best tools available, and would be exponentially better than a sloppy trainer with a poorly trained dog.
But, pork carcasses are used for training scents when trainers can't or wont jump through the hoops they have to to get human cadaver scent. And pseudo-scents are used as well, though not too much anymore. This is a really good (old) article on it:
http://discovermagazine.com/1996/mar/thefakesmellofde714
Human is best.
Pork is probably next best. I would hope that KCMO has human-trained dogs available, but as you said - who knows how the particular dog that made the hit in this case was trained?
If all LE was looking for was a hit - any hit - to get probable cause for a warrant, they might not have brought the best trained dog to the scene. If they were legitimately checking for human decomp, then they probably would have gotten the best out there. Unfortunately, since we don't know what they do, we have no way of knowing what they were going for.