To be fair to him, it could be implemented if he was trying to 'compress' something not particularly complex (as you said below: "And 100 bytes would only answer some hypothetical original size threshold"), and/or something *not* totally arbitrary (the makers of 'the produkkt' were able to store the instructions *specific to their game*, but they did not write software that could compress *any* arbitrary file). He is has a procedural approach, where instead of building a dictionary/table of terms/codes/sequences, he is instead trying to write a program that can basically generate mathematical expressions/equations that, when called, produce the proper sequences that represent the original data. This is somewhat described on 'the produkkt' (link above):
Yep. That is unrealistic. More, it's most probably impossible, unless we find some other form of storing data (maybe quantum hard drives).