I think they were nitpicking the term "reverse engineering" which is fair if the source is available

The source was available, but with cryptic variable names and (apparently) no or little comments:

> Ward mentioned that the biggest bottleneck was the cryptic variable names—short abbreviations that were common in old-school programming but made the code nearly impossible to follow.

> "He not only commented everything," Ward marveled, "he went through every single line of code and renamed every single variable for me in about three days.

I think it's still fair to use the term "reverse engineering".

Meh, every time a new engineer joins a large project onboarding is actually reverse engineering, with luck assisted by original authors.