The whole “police dog” comparison is completely misleading. Drugs dogs are hilariously unreliable and are explicitly used by some departments solely to create probable cause.
And with SAR dogs, they don’t need to be reliable at tracking as long as they are better than humans.
"Drugs dogs are hilariously unreliable and are explicitly used by some departments solely to create probable cause."[0][1][2]
[0] https://en.wikipedia.org/wiki/Florida_v._Harris
[1] https://www.utahcriminallaw.net/drug-sniffer-dog-false-posit...
[2] https://www.smh.com.au/environment/conservation/sniffer-dogs...
Just looking at airport stats isn't enough. A drug dog might sniff trace amounts of drugs on clothing, but a search may not turn up anything because the trace amounts are from days earlier. Or maybe the contraband is too well hidden to be found, and so the drug dog's signal is labelled a "false positive" because the search failed even though it really was a true positive.
Even if a drug dog is only right 50% of the time, that's still pretty incredible odds unless literally 50% of the population is carrying illegal drugs at any given time.
I'm not saying that I don't believe drug dogs used as an excuse to manufacture probable cause, but I also don't believe the concept of an accurate drug-sniffing dog is impossible, considering blood hounds can detect and follow extremely dilute traces of a person's scent.