Auto-repartnering isn't intended as a trap. It's a convenience option for people who want to keep the same pair of cats breeding without having to re-partner them after each successful breeding. Auto-repartnering will expire if the two cats do not produce a kitten within the 11 day time frame. We extended the partnership period to accommodate people that do not breed their cats every 7 days since they don't use the milk/cuddle buff.
In situations where a cat is partnered to another cat that was sent to the menagerie (or perma-petted) you can send the remaining cat to the cattery and use a break-up drink there. This functionality will eventually be available with in-world break up drinks but will require an update first.
Going back to my first statement, the idea of convenience products or features is something very important to us at KittyCatS. It is entirely possible to "play" the KittyCatS "game" without spending anything other that what you would spend on food. Our other products - Vita-Milk, various vitamins, Perma Pet, the HUD, the auto-feeder, etc. - are what we consider "convenience products". If you purchase them, you are basically purchasing the convenience it provides; in the case of the break up drink, that would be the convenience of breaking a partnership RIGHT NOW instead of waiting it out. Remember, even though we make heavy use of convenience products and features, we also provide many zero-cost alternatives to our customers.
I think of it like a toll road. I could drive on the highway for free, or pay to take the toll road and get to my destination quicker and with less hassle. It's a personal choice.