This is interesting. I remember coming through MCO a couple of years ago; the security line was ridiculously long and barely moving. After waiting 30+ minutes we were only just ahead of the boarding pass / passport checkpoint. Then all of a sudden, it was as if floodgates opened. The line started moving along at a decent clip, and security staff were adamant that everyone should keep their shoes and jackets on and put absolutely everything inside their carry-on luggage. We ended up walking through security almost as though it wasn't there. Our bags went through the machine seemingly without a pause. I thought the whole experience was very bizarre - it was like they just gave up.
But there was a dog there. I didn't think anything of it at the time, just assumed the dog had been there all along. But now that you mention this, perhaps the dog had just arrived, and that made all the difference? That would make more sense than my "they gave up" theory.
Too bad they don't have the dogs around all the time. I much preferred that to the usual routine!
