If you can find the corresponding definition in the header files, you can use this. As far as I know the ArduinoIDE also uses these to include the right header files for each target. If you want to create code, that is reusable both on Uno and ATTiny, than I would suggest to use a combination of #define and #ifdef, #ifndef and #endif directives, so that depending on a defined flag only the corresponding code is compiled. If you just want to pretent, that it would really be the Wire library, this might not be a good coding practice, since this somewhat hides the fact in your code, that you use not the Wire library, but a different library. I don't understand completely, why you want to rename the TinyWireM library to Wire. The TinyWireM library shows almost the same behavior as the Wire library on the Uno, but is not the same library ported to the ATTiny.

The Wire Library doesn't work on the ATTiny, because it has only a USI (Universal Serial Interface), which is not the same hardware as in the Arduino Uno.

Wire library arduino