No doubt.
As at least i believe you, @Gus_Issa, are aware, there has been some talk about the proper strategy to extend things such as these controllers. Simple inheritance fails as there also has been question regarding the extensive use of sealed classes. (You even introduced the library bug asking the same question.)
In this particular post you gave a like to the comment suggesting the implementation of the provider interface as a way to perhaps properly extend the UART controller for the OPs purpose.
So my confusion is really in the belief that implementation of these interfaces must be the intended method to extend functionality. Please bear with me as I now come to the understanding that is not the case.
I can understand such functionality is low on the to do list, and wont assume what it takes to determine a safe or feasible change. But at least my recent pull drafts exercise the external implementation of IGpioControllerProvider, and demonstrate how limited a change is needed.
Ultimately things may not be feasible for TinyClr, it would just be cool to feel we’re all on the same page. Not understanding custom provider implementation was never an available option feels like not being on the same page…