I think you may have missed it, Horus was able to take some of Seth's semen and showed it to his mother. Isis was enraged and cut her son's arm and jerked him off and placed his cum into a jar (HAHAHAHAHA)
Here is the actual writing from the link
Isis at morning time went carrying the semen of Horus to the garden of Seth and said to Seth’s gardener: “What sort of vegetable is it that Seth eats here in your company?” So the gardener told her: “He doesn’t eat any vegetable here in my company except lettuce.” And Isis added the semen of Horus onto it. Seth returned according to his daily habit and ate the lettuce, which he regularly ate. Thereupon he became pregnant with the semen of Horus.

This is how the actual myth really went, it's explained really well, I do recommend some of you read it (it's short) while waiting for the next update.
Alsoo, Seth got pregnant?!!
https://www.google.com/amp/s/www.thenotsoinnocentsabroad.com/blog/horus-vs-seth-homosexuality-hippos-and-familial-violence%3fformat=amp