The Golden Visa is sold as investment-for-residency, but the real first step is a tax number for everyone on the application.
No Greek bank will receive your investment funds, and no notary will sign your purchase, until each applicant holds an AFM. That makes the tax number, not the property, the true starting line of a Golden Visa.
Because the visa extends to a spouse, children and often parents, every one of them needs their own number. Registering the whole family together is what keeps a submission from stalling on a single missing applicant.