Animals are not pre-programmed single chip computers. Behaviors are learned and experience gained over time.Not so, virgin dogs may even panic when they find they cannot disengage.
Not entirely. Ejaculation continues long after knotting. The first and second fractions happen fast so that semen delivery is accomplished quickly. During the tie the male ejaculates 3rd fraction and that can continue for up to several dozens of minutes to ensure successful fertilization.Supposedly he will already have gotten his O and lost interest long before he can escape a tie, which is why he tries to dismount and move away.
Stimulating the knot in a tied position often even makes the dog squirt more clear liquid even after he stopped before.
You can quite clearly observe the reaction to stimulation in this position.
You stop, the anal contractions stop and the tip stops twitching. You resume and all of it resumes. This is usually accompanied with closed eyes and relaxed facial expression which is visibly changing in reaction to stimulation in the tied position.