Ok, maybe you right. Thank you for your opinion.
But to be honest with you, I don't care. The subject wasn't the authenticity and date of the certificate, and in posting this, I didn't think I would be called a liar.
To be clear, I deposited the sword at the NBTHK in September 2020, and received the certificate in early March 2021. An NBTHK certificate is not issued in a week.
That's all. End of the story.