Compiling Android takes many hours and requires a lot of RAM and disk space, more than I have available on my machines right now. For some things there, binary patching may actually be an easier way to change stuff than compiling the whole thing from source.
Now scale that up and consider - at which point such project would start being "FOSS" in your book without actually providing its sources on an appropriate license?
The intention behind "preferred form for modification" is to put you as a user on the same level as the copyright holder. This construct works well in a world where compiling is cheap; where it isn't, it may require some refinement to preserve the intention behind it. The copyright holder could decide to modify the learning set before pressing the "start" button, you can't.
Now scale that up and consider - at which point such project would start being "FOSS" in your book without actually providing its sources on an appropriate license?
The intention behind "preferred form for modification" is to put you as a user on the same level as the copyright holder. This construct works well in a world where compiling is cheap; where it isn't, it may require some refinement to preserve the intention behind it. The copyright holder could decide to modify the learning set before pressing the "start" button, you can't.