Like Spring Fever I have extensive experience in this regard and feel like I should weigh in. I am a long haul pilot flying widebodies across the Pacific for close to 25 years. We generally follow a series of organized tracks called the NOPAC routes and as a result, West and East bound traffic can become quite stacked up. It’s not uncommon to be in the middle of the North Pacific (middle of nowhere) and be literally surrounded by other aircraft, only separated by 1000’ vertically.
What this concentration of aircraft allows, is a close examination of contrail formation and breakup. Contrails vary in intensity and sometimes won’t be forming at all. This will depend on environmental conditions, like temperature, relative humidity and upper level winds. One aircraft 1000’ above you will be leaving very distinct trails while another 1000’ below, won’t be leaving any trail at all. I have watched hundreds of aircraft ahead and above me for hours at a time, they will generate contrails for hours or minutes and the trails will abruptly terminate, only to start up again at some random time again. This is due to the variability of the environmental conditions. When you are traveling at 550 mph, you transverse various conditions quickly, which is not apparent from a ground perspective. Upper level winds regularily exceed 200 mph and will break up a contrail rapidly. This break up can take many forms and may appear as the OP suggests. Vortices are the result of the creation of lift on a wing and can cause issues, ranging from mild turbulence to aircraft upset close to the ground, resulting in a hull loss. The vortices can carry the contrails with them and descend at an average speed of 500 feet per minute and are usually benign within a couple of minutes (2000’) Just because the vortices aren’t a concern to us for safety anymore, doesn’t mean they don’t continue to descend for another few thousand feet, carrying with them the moisture in the contrails with them.
If I were to make an educated hypotheses, I would say the aircraft over Victoria are flying at an altitude and in conditions that promote a solid formation of contrails. At the same time, I would also assume the upper level winds were light and not prone to disrupting the contrails, thus allowing the trails to disperse and descend without breaking up.
Spring Fever, sounds like you and I would share a number of friends.