Oh yeah, that would make sense. In his mind, you’d crossed a territory line. The line was invisible to you, but very real to him. Once you lifted him across the line, you weren’t crossing it any longer.
Years ago, I read in the paper about a case in which somebody got badly bitten; and neither the person bitten, nor the one writing the article, nor the dog’s human had any idea why, though it was immediately obvious to me.
The dog routinely rode in his human’s truck. The human drove, with the dog in the truck, to his worksite. When they got there, the human and the dog both got out of the truck. One of the other workers came over; the humans talked, the other worker patted the dog, everything was fine.
Then the dog was put back in the truck (suitable temperatures, apparently, and probably windows down) and the two of them went to work. After a bit, a tool was needed. The dog’s human had one in his truck – and told the other worker to go and get it out of the truck.
New acquaintance, dog’s human not present, opened the door of the truck with the dog in it and started to take the tool. Dog bit.
– well, yeah. The space outside of the truck wasn’t the dog’s, or his human’s, territory. It was neutral ground. And the dog’s human was present. That the dog was quite willing to be patted in that situation didn’t mean he wouldn’t attack someone who, from the dog’s point of view, was breaking into his house and stealing stuff!
Only time I ever had a dog seriously try to bite me was once when I was walking past a house on the sidewalk, and a Very Small Dog came charging out of the yard and did his very best to bite my leg.
It was a Very Small Dog and I had on thick leather boots. The dog couldn’t get through, and couldn’t reach high enough to bite above them. But was certainly trying.
– another time I was walking down the road some distance out of town and a quite large dog came running at me in what actually was full threatening charge mode: silent, fur bristling, teeth bare, ears full forward or full back I don’t remember which, tail flat. I knew better than to run, but was so startled that I just stood utterly stock still with my arms down – which turned out to be the right move. As he got close, he appeared to realize that I wasn’t behaving either like prey or like a threat; he put on the brakes, and literally skidded to a stop right in front of me, so close that his bared teeth banged into my leg hard enough to leave a bruise; but he didn’t actually bite.
At which point his human appeared, frantically calling him; which worked.
– I’ve also had two very large dogs come running at me out in a vineyard. Entirely different body language, not aggressive at all; but I was really glad I knew enough Dog to tell. They sniffed, I patted, everybody was fine.