Employment Law Questions? Ask an Employment Lawyer.
What you read was wrong, EEOC charges are amendable to until the conclusion of their investigation. You generally only need to allege a basic factual scenario that indicates why you believe you were discriminated against on account of your age, race, gender, disability or religion (or any combination of these) to make a valid EEOC complaint. The Agency then contacts the employer and has them submit a position statement as to their side of the story. They often also request documents and to speak with management or others at the employer that may be material witnesses to the discrimination. You don't really need an attorney for any of this, but many people do retain one anyway I think because they feel more comfortable that way.