Hello Dr.,
From what I understand topping auto's is a no go, they're essentially designed to go from seed to harvest in a given amount of time. When you top the plant you're essentially adding recovery time on which you do not essentially have, while also adding stress. The whole point of topping is to redirect the hormones from a single point to multiple points. In theory this would allow the lower portions of your plant to catch up and result in multiple tops of equal size and weight. However, auto's are not going to give you the required time for the lower portions to develop, they will simply follow their genetics and begin to flower. Here is an article from dutch passion regarding the topic. https://dutch-passion.blog/topping-autoflowers-for-yield-good-or-bad-idea/ .
Now, in the future if you plan to grow with autos which appears to be very popular on this particular site, I would recommend lower stress techniques. The first would simply be FIM'ing, while similar to topping it is much less stressful and actually results in more tops and a bushier structure than topping. Finally, you could have simply pulled down the main cola and tied it to the side of your container in an attempt to LST. This would have redirected the growth hormones and allowed the lower portion to mature. Both techniques signal to your plant that the vertical growth limit has been reached, and to survive it needs to develop its lower foliage. Here's an article on training in general, I would give it a good read and find out what's in your best interest moving forward https://www.zamnesia.com/grow-weed/58-fimming-cannabis . Hope this helps, and good luck.