I have always peed first and then defecated. It never occurred to me to try the reverse order.

I have the same experience and always assumed it was caused by bowel contents putting pressure on the urethra in/around the prostate. I’d be interested to learn if there’s anything more to it than that and if it’s a uniquely male experience… (I assume you’re male?)

I believe this website explains it best.

https://motivatetherapy.com/2017/01/is-it-normal-to-pee-and-poo-at-the-same-time/

The real question is can you shit and prevent yourself from peeing if you have a full tank.