Yes, I link to a different version of that same file in the article (my link points to the version hosted on kernel.org, rather than Github). It provides a bit of high-level context, but by itself it doesn't provide enough detail to actually reimplement the corresponding Git functions.
Aside from being more terse and (IMHO) more difficult to read than prose with examples and non-ASCII diagrams, that file doesn't explain the context and motivation for packfiles, and it doesn't cover the parsing and application of deltas at all.
If you found that piece of documentation deficient while implementing a packfile parser, then it would be nice to update it to include those details that were lacking to help the next person to reimplement git.
