(I don't actually expect it to have such staunch opponents, though, so the misclassification is probably due to other reasons.)
https://publiccode.eu/ and the current legislation trends in the EU are not fun, because they are not able to drive the narrative.
Second, even if publiccode.eu doesn't help Facebook in any way, that's not evidence that they have motive to intentionally block it. You'd have to demonstrate that they have some reason to want the initiative to fail, not just claim they don't care.
So the React ecosystem is smoke and mirrors? GraphQL?
Same as GP, I don't see what interest Facebook would have in blocking this initiative. The impact the initiative would have would have very little impact on Facebook's business. Their moat is their userbase and no amount of good "public code" would change that.