For example, if you do end up needing compression, are you going to write you own compression library or use an existing one somebody else already wrote?
I think you're missing the point. I'm talking about the concept of mathematically modelling the program first, before writing it (as per the article). This process only applies to certain types of applications, ones that are rooted in algorithmic transformations (like compression), rather than in system and I/O operations, like copying a packet from a network RX buffer into a disk block, in the most efficient way.