None of these reasons address your concern.
1) Certificates don’t count as credit, it’s a cheap way of getting around credit.
2) Yes.
3) Double blind is an initial review process, once the paper is published everyone in the effort should be credited. Not always as an author, but credit on paper is due.
Sorry this happened to you.
Please let us know if you are planning to replace your engineers with AI, so we may stop using your product.
Focus on quality engineering, not code writers.
I will be actually impressed when an AI system (LLM/agentic, or whatever you like behind it) solves an open math problem.
Until then, in my head they just recycle information that is already provided by humans and ofc are very smart search engines.