I doubt anyone completely understands the process

I doubt anyone completely understands the process that breaks down either, is the point. All anyone knows is that things that get broken down in the liver drastically change form and function, and there's a list several miles long of drugs that have been found to run afoul of human biology at some point during that process.

You're being glib about it being "so well known" when it really is:

https://www.aafp.org/afp/2007/0801/p391.html

YOU may not be familiar with this, but anyone in the pharma world is. Again, the exercise is left to the reader. If The Reader chooses not to pursue, that's on Them.