if you read the post, it mentions the dog wouldn't go BACK under the seat...this indicates to me that the dog had been under the seat prior to this time
therefor the dog had "fit" under the seat.
obviously dog lovers will try to stay on the dog's side...but this has been done for YEARS with no problem for the dog or master.
capot, if the dog is laying down it fits under the seat and I have seen it done...even on a turboprop the size of a metroliner.and if I recall properly, the blind man and dog is afforded the chair with the most leg room in the whole plane (middle seat last row).