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.
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.