It looks like this is trying to fit into the same space as the former USDS and F18 which had term appointments. The key idea behind those was the industry partnership (recruiting experienced people from industry) and the knowledge/skills transfer that came with it. If you look at some other programs (Peace Corps, for instance) you'll see a similar thing. 2-year terms with extensions up to maybe 5 total years.
What's funny is the retirement benefits won't apply to most 2-year term employees. Unless they were prior military or civil service, or come back later, two years is not long enough to keep the TSP match (three year vesting period) or to qualify for the pension (five years). (EDIT: Funny because they explicitly list it as a benefit, but these folks won't qualify for it.)
The funny thing here is that the short (often 1-3 years) tenure that's so common in the industry leads to some absolute dogshit software. Good things take time. By limiting terms to 2 years you almost guarantee that outcome.
The biggest red flag on engineering resumes is never sticking at something for more than 2 years. Your bad decisions never catch up to you.
