The term 'Manhattan Project' is a common and widely used metaphor for R&D programs with effectively unlimited resources applied to them. The actual Manhattan Project is simply a very famous exemplar of such a program.

Use of that term is not propaganda, it's normal English.

When referring to the efforts nation-states, I'd be very interested to hear how often such metaphorical usage is used to describe the work of adversarial vs. friendly countries. I would be shocked if it's as often (in the Anglophone press) used to describe the work of US-aligned countries as it is that of US-adversarial countries.

This is literally by the country that suffered the most from it.

Well, the description is attributed to "two people with knowledge of the project" of unclear national origin.

It's not just about the use of the term "Manhattan Project". It's about the framing and wording of the article. There is literally an image of a PRC soldier in front of a rocket in the article.