Villain's play would be totally out of line with a K,and overbet shoving and showing the nuts is even worse.
I would have totally agreed with you until about a month ago and still do unless it is early on in tournaments that tend to have a fair amount of fish/donks. I play in a lot of live tournaments where you have a lot of people doing really stupid stuff early in tournaments. One guy that i play with in the same tournaments was always doubling up early on before the first break. I finally asked him how he was running so hot and he laughed and said i have been shoving the nuts. I laughed and thought what a donk. Then three weeks later we are at the same table and sure enough he moves all in on the turn and a solid Reg. calls. He turns over the straight and the reg has a set. Straigt holds for the win. I also know the Reg and at the break he was still waiting for a cash game and he was steamed. It he kept saying what kind of donk shoves i thought "x" (the guy who shoved) was a solid player.
So after the tournament i took "x" out for a beer and picked his brain. I found his rational was not totally crazy. In the first two rounds blinds are small we start with a 1/100 blinds structure. So we started to do some math and running several scenarios. After either flopping a large hand or getting one on the turn what do you really make early on in these tournaments? Not that much unless it is big hand vs. big hand. The board normally gets scary or it is so dry that the action also dries up. So if you make 20% how much does that help you in the long run compared to doubling up early on?
I almost never show my hand. He has always been showing the nuts. His reasoning is that it helps him later with the less experience players and I feel he has been shoving light against regs lately. I know on Sunday when I had top two pair he was light but I just couldn’t call.
A final thought about the JAQ flop. I had a similar situation occur a while back where UTG raised 3bb three people called and I called from the big blind with Kd10d. The flop came AdQsJd. I checked and UTG bet 2/3 pot and with one other caller and I called. The 10c came on the turn and I checked again and UTG bet the pot. I shoved thinking the UTG had the straight and we would probable split the pot plus I was on a freeroll with the diamond draw. If the diamond came on the river I wouldn’t be able to get anymore from him but I thought he would call the all in on the turn. He called and we split the pot.