A certificate is a compressed claim: this person completed this syllabus and was assessed on it. Its value comes entirely from whether a stranger can check that claim without taking your word for it.
That is why the registry matters more than the PDF. At Certalyx every certificate carries a unique ID, a signature generated with a key held only on the server, and a chained record in the registry. Anyone can enter the ID and see whether it was issued, to whom, for which programme, and whether it has since been revoked.
What it does not prove is equally important. It is not a licence, not a degree, and not a guarantee of work. It says nothing about you outside the syllabus it names. A certificate that overclaims is worse than none, because the first person who checks it catches the exaggeration.
For someone entering AI data work from Kenya or Nigeria, the practical benefit is narrower and more useful: it replaces an empty profile with evidence. It shortens the conversation with a vendor from an unanswerable question about ability to a question about availability.